* Lebanon says Israeli drones threaten sovereignty
* First such incident in more than 10 years
* Tensions rise in Middle East (Recasts with Nasrallah)
By Laila Bassam and Jeffrey Heller
BEIRUT/JERUSALEM, Aug 25 (Reuters) - Hezbollah leader Sayyed Hassan Nasrallah said on Sunday the fall of two Israeli drones overnight in suburbs of Beirut dominated by the Iranian-backed group amounted to a very dangerous move.
Nasrallah, whose group fought a month-long war with Israel in 2006, said in a televised speech: "The latest Israeli development (is) very, very, very dangerous."
There were no signs the bitter enemies were headed for a conflict. But Lebanese Prime Minister Saad Hariri said the drones were designed to stir up regional tensions.
In the first such incident in more than a decade, one drone fell and second exploded before dawn near the ground and caused some damage to Hezbollah's media centre in the Dahiyeh suburbs, a Hezbollah official told Reuters.
"The new aggression...constitutes a threat to regional stability and an attempt to push the situation towards further tension," Hariri said in a statement from his office.
The Israeli military declined to comment.
The incident took place hours after the Israeli military said its aircraft had struck Iranian forces and Shi'ite militias near Syria's capital Damascus which it said had been planning to launch "killer drones" into Israel.
War monitor the Syrian Observatory for Human Rights said two members of Hezbollah and one Iranian were killed in the Israeli strikes around Damascus.
The Israeli military said its aircraft struck "Iranian Quds Force operatives and Shi'ite militias which were preparing to advance attack plans targeting sites in Israel from within Syria over the last number of days".
The elite Quds Force is the overseas arm of Iran's Islamic Revolutionary Guards Corps (IRGC).
"KILL HIM FIRST"
"Iran has no immunity anywhere. Our forces operate in every sector against the Iranian aggression," said Israeli Prime Minister Benjamin Netanyahu on Twitter. "If someone rises up to kill you, kill him first."
In Tehran, a senior Revolutionary Guards commander denied that Iranian targets had been hit in the Israeli air strikes in Syria, the semi-official ILNA news agency reported.
Israel deems Lebanon's heavily armed Shi'ite Hezbollah movement, backed by Iran, the biggest threat across its border. In their 2006 war nearly 1,200 people, mostly civilians, died in Lebanon and 158 people died in Israel, mostly soldiers.
Lebanon has complained to the United Nations about Israeli planes regularly violating its airspace in recent years.
Residents in Dahiyeh said they heard the sound of a blast. A witness said the army closed off the streets where a fire had started. A Hezbollah spokesman told Lebanon's state news agency NNA the second drone was rigged with explosives causing serious damage to the media centre.
Hezbollah is now examining the first drone, he said. The Lebanese army said that one Israeli drone fell and another exploded at 02:30 am local time (2330 GMT), causing only material damage.
"The army arrived immediately and cordoned off the area where the two drones fell," it said.
Israel has grown alarmed by the rising influence of its regional foe Iran during the war in neighbouring Syria, where Tehran and Hezbollah provide military help to Damascus.
Israel says its air force has carried out hundreds of strikes in Syria against what it calls Iranian targets and arms transfers to Hezbollah.
Iran and Hezbollah are helping President Bashar al-Assad in the eight-year-old Syria war. Russia, which is also aiding Assad, has largely turned a blind eye to the Israeli air strikes
Syrian state media said air defences confronted the "aggression" and the army said most of the Israeli missiles were destroyed.
The United States and Iran are at odds over Tehran's nuclear programme and the Gulf, with both sides trading accusations over threats to the strategic waterway's security.
Iran also has wide sway in Iraq.
Iraq's paramilitary groups on Wednesday blamed a series of recent blasts at their weapons depots and bases on the United States and Israel.
The Popular Mobilisation Forces (PMF), the grouping of Iraq's mostly Shi'ite Muslim paramilitary groups, many of which are backed by Iran, said the United States had allowed four Israeli drones to enter the region accompanying U.S. forces and carry out missions on Iraqi territory.
Netanyahu has hinted of possible Israeli involvement in attacks against Iranian-linked targets in Iraq.
On the Israeli YNet news website, military affairs commentator Ron Ben-Yishai described the alleged Iranian killer drone attack plans as revenge by Tehran for the purported Israeli drone strikes in Iraq.
Amos Yadlin, a former head of Israeli military intelligence, said neither Iran nor Israel were interested in all-out war.
"We're not there yet," he said on Israel Radio. "But sometimes, someone makes a mistake."
(Additional reporting by Lisa Barrington, Leila Bassam, Ellen Francis, Stephen Farrell, Maayan Lubell and Kinda Makieh and Samar Hassan; Writing by Michael Georgy; Editing by Angus MacSwan, William Maclean)