* Muslims from North Caucasus see jihad in Syria
* Russia says hundreds of its own fighting with al-Qaeda-linked rebels
* Experts warn they will return - trained in warfare - to fight Russia
* Say they could strike during Russia's hosting of 2014 Olympics
By Alissa de Carbonnel
NOVOSASITLI, Russia, Nov 14 (Reuters) - A scrawny 15-year-old this summer became the first from his deeply religious Muslim village in Russia's southern Dagestan province to die fighting alongside rebels in Syria.
Some regard him as a martyr for joining the rebels in the fight against Syrian President Bashar al-Assad who is supported by Russia.
Moscow now fears that hundreds of Russian-born militants it says are fighting in Syria will return experienced in warfare to join an insurgency in Dagestan and its other North Caucasus provinces by militants fighting for an Islamic state.
Violence in the region claims lives almost daily. Fifteen men from Novosasitli alone have died in shootouts with Russian forces in the last four years, locals say.
Analysts say fighters could also try to strike during the 2014 Winter Olympics in February in nearby Sochi. President Vladimir Putin, who has staked his reputation on the Games, has said militants returning from Syria pose "a very real" threat and signed off on a law this month to jail any who come home.
"The militant groups did not come out of nowhere, and they will not vanish into thin air," Putin said on Sept 23.
In Novosasitli, where walls are tagged with graffiti supporting rebels fighting for an Islamic state, villagers say at least eight out of 2,000 inhabitants have gone to Syria.
"There are whole brigades of our boys there," village council member Akhmed Khaibulayev said.
Three of them were arrested by Russian forces on their way home via a land route crossing the border from Azerbaijan back into Dagestan, he said, but five have returned, underscoring the ease with which Russians travel to and from Syria.
"They are at home now, waiting for when the security forces come for them," Khaibulayev said.
Anxious parents try to hold back their sons.
"A father knows his son. I told him to leave his passport with me. When he refused, I took it away," a man dressed in a beige tunic and skullcap said, asking not to be named for fear of reprisal by Russian security forces.
Despite his warnings, his 23-year-old son, whom he boasts knew the Koran by heart, left two months ago for the battlefield. "I don't know if he will come back," he said.
A photograph, sent by fighters, of the scarred, skinny corpse of the local 15-year-old killed there is still being passed around the village. Stones are placed over his eyelids.
In the comment thread under a photo of the smooth-chinned youth on a Facebook page he is called a hero and a martyr.
"He went to Syria because he couldn't stand that Assad and his army were killing children," said a villager, who locals said also fought in Syria and who refused to be named.
The boy had studied in Egypt before joining other Russian-born militants in Syria, and his family only learned he had gone to fight there after his death, locals said.
His father, who lost an arm in Syria when he went to see his son's grave, was briefly detained by security forces in August when he returned home. He refused to speak to Reuters.
The sons of Novosasitli grew up playing "cops and insurgents" in the streets. Russian rule is tenuous with residents describing police as the enemy, the state as corrupt and say they manage their own affairs under Sharia law.
Some have had relatives, classmates or neighbours join Islamist insurgency in Russia, rooted in separatist wars in neighbouring Chechnya.
The militants adhere to Salafism, an ultra-conservative branch of Sunni Islam. They do not have the support of all Salafis - some disapprove of their racketeering ways or do not view their attacks on police and officials as a lawful jihad.
The battle raging in Syria is different. It is widely seen in the majority Sunni Muslim region as a "true" holy war against Assad's Alawite-dominated government.
But voicing that support for Syrian rebels in Russia is dangerous. A popular young imam who had raised funds to help Syrian refugees has fled to Turkey after coming under pressure from law enforcement. Media with links to police claimed he was inciting youths to join the conflict.
The doors of a newly built, emerald-domed madrasa he ran in Novosasitli now stand shut, empty of students.
"There's no obligation for Muslims to go from here to Syria," says Abdurakhim Magomedov, 71, a Salafi scholar in Novosasitli. "But if someone wants to go, no one can stop him."
THREAT TO OLYMPICS?
The flow of Russians from the North Caucasus going to Syria increased this year, officials and locals say, as pleas for help from rebels grew more acute following a poison gas attack in the suburbs of Damascus.
In June, Russia's FSB security service said 200 Russians were fighting with al Qaeda affiliated groups in Syria. By September, it said as many as 400 Russians were there.
"They will come back, and that poses a huge threat," FSB deputy director Sergei Smirnov, said on Sept. 20.
Russian estimates of the number of fighters may not be accurate, experts say, because of the large numbers of its citizens studying abroad or who have emigrated to Europe, Jordan, Turkey and elsewhere.
Some gained skill and experience, highly-valued by the Syrian rebels, in fighting the separatist wars in Chechnya in 1994-96 and 1999-2000, Afghanistan and elsewhere.
Experts say the number of Russians in Syria may be higher.
Russia's protection of Assad, with weapons supplies and diplomatic backing, has also left many angry at Putin.
"Muslims the world over revile Putin for his support of Assad," said Dzhabrail Magomedov, one of some two dozen in Novosasitli, who studied at a religious school in Damascus.
This summer the Chechen-born Caucasus insurgent leader Doku Umarov urged fighters to use "maximum force" to sabotage the Olympics. His cry was echoed by fighters in Syria, who called on Muslims in the North Caucasus to wage jihad at home rather than joining them.
Russia has a history of recent militant attacks. Suicide bombings in the past two years killed dozens at a Moscow airport and subway. More than 380 people, mainly school children, were killed in the siege of a primary school in Beslan in 2004.
"For such a jihad, one, two people is enough," a Russian-speaking rebel says in a YouTube address from Syria dated July 30, flanked by seven camouflage-clad fighters armed with heavy machine guns and a grenade launcher.
Security is tight around Olympic host city Sochi, which abuts the North Caucasus region.
"Do you know where Sochi is? We have enough of our own rebels there," said Sergey Goncharov, a former deputy head of the FSB's elite Alfa counter-insurgency unit. "If they now get reinforcement from Syria, our security services will be hard put to prevent them from ruining the Olympics."
An amendment to Russia's anti-terrorism law, submitted by Putin and rushed through parliament after a deadly bus bombing killed six people in southern Russia on Oct. 21, makes those who fight abroad criminally accountable at home.
Under the law, training "with the aim of carrying out terrorist activity" is punishable by 10 years in jail and being part of an armed group abroad "whose aims are contrary to Russian interests" by six years in jail.
'OUR MUSLIM BROTHERS'
Since Putin rose to power 13 years ago and crushed a Chechen separatist revolt, he has said he would not allow the Caucasus provinces to split from Russia.
But the nationalist cause that inspired Chechens to revolt after collapse of the Soviet Union has mutated into an Islamic one that spread to nearby Caucasus mountain lands.
Defeated in Chechnya, rebels now launch near-daily attacks in Ingushetia, Dagestan and Kabardino-Balkaria. Today, the ranks of fighters are filled by youths disillusioned by police brutality, joblessness, corruption and the perceived persecution of religious conservatives.
Empathy for fellow Sunni Muslims caught in the bloodshed in Syria is especially sharp among Chechens, who see in it echoes of their own suffering in two wars for secession from Russia.
"They also killed our mothers, brothers and grandparents," said Akhmed, a 21-year-old Chechen, in the village of Berdykel, near the provincial capital, Grozny. "We want to help. They are our Muslim brothers."
In response, Chechen authorities have banned wakes for anyone killed in Syria, and Muslim clerics speak out in mosques and schools, casting the war as a political struggle not a religious one. A local government minister was fired when one of his family left for Syria, a source who knew of the incident said.
Chechen-language TV aired the apology of a 26-year-old, who said he had made a mistake fighting to Syria and doubted the war was a true jihad because of infighting among the rebels.
"I got scared that I would die not on the right path, so I came back," he said, head bowed before Kremlin-backed Chechen leader Ramzan Kadyrov.
At his yellow-gated home in Berdykel, a relative said his family no longer let him live at home. "It's very painful for us," said a young male relative. (Editing by Anna Willard)