(Adds retailers, British consulate employee; paragraphs 16-17, 21)
* Jewel traders want huge trade fair postponed
* Leading banks take out ads calling for law and order
* Airport again targeted in weekend protests
By Twinnie Siu and Donny Kwok
HONG KONG, Aug 22 (Reuters) - Hong Kong banks published full-page newspaper ads calling for law and order in the Chinese-ruled city and international jewellers sought the rescheduling of a huge trade fair as weeks of pro-democracy protests showed no sign of let-up on Thursday.
Thousands held a scrappy anti-government protest on Wednesday at a suburban subway station where demonstrators were attacked by a mob of white-shirted men last month.
Protesters at the subway station were angry that nobody had yet been prosecuted for that violence. Police said they charged two men with rioting in connection with the July attack, who are to appear in court on Friday.
Wednesday's standoff stopped short of recent intense clashes, including the storming of the legislature and occupation of the airport, with police refraining from using tear gas or attempting to storm protesters' lines. Police said they arrested two men for unlawful assembly.
HSBC, Standard Chartered and Bank of East Asia all urged the restoration of order in the former British colony, which returned to Chinese rule in 1997.
"Oppose violence, restore social order, safeguard Hong Kong's status as an international financial centre," Standard Chartered said in its advertisement.
Trade representatives of the world’s largest diamond trading centres, from Antwerp, Mumbai and Ramat Gan, asked the organiser of the high-profile Hong Kong Jewellery and Gem Fair to postpone the event, which typically draws more than 54,000 visitors.
In a letter, they told organiser Informa Markets that between 30% and 40% of exhibitors were demanding to pull out of the fair, due to be held in September at the Asia World Exposition centre and the Wan Chai Convention and Exhibition centre.
"In light of recent events, we urge Informa Markets to consider the following; rather than potentially risking an empty show in terms of both visitors and exhibitors, postpone the show to a later date - as yet to be determined - once Hong Kong is in a more stable climate," the representatives wrote.
"Additionally, we request financial compensation in the form of a discount or refund for all participating companies."
AIRPORT 'STRESS TEST'
Protests erupted in Hong Kong in June over a now-suspended bill that would allow criminal suspects in Hong Kong to be extradited to mainland China for trial but have since grown into one of the biggest populist challenges faced by Chinese President Xi Jinping since he took power in 2012.
The unrest has been fuelled by broader worries about the erosion of freedoms guaranteed under the "one country, two systems" formula adopted after 1997 but not enjoyed on the mainland, including an independent judiciary and the right to protest.
Several anti-government demonstrations are planned, including a rally by hundreds of high school students on Thursday and a "stress test" of the airport at the weekend.
The protests are already exacting a toll on Hong Kong's economy and tourism, with the financial hub on the verge of its first recession in a decade.
The Hong Kong Retail Management Association, which represents more than 8,000 businesses, urged all landlords to halve rents for six months.
"If the situation continues, it is expected that many retailers may have to sack staff or even shut down," it said in a statement.
Hong Kong leader Carrie Lam reiterated on Tuesday that the extradition legislation was dead but has stopped short of officially withdrawing the bill, as protesters have demanded.
Demonstrators are also calling for an independent inquiry into the protests and perceived police brutality, a halt to descriptions of the protests as "rioting", the waiver of charges against those arrested, and resumption of political reform.
Beijing has reacted sharply to the protests and accused foreign countries, including the United States, of fomenting unrest. China has also sent a clear warning that forceful intervention is possible, with paramilitary forces holding drills in neighbouring Shenzhen.
An employee of the British consulate in Hong Kong has been detained in China for involvement in prostitution, the state-backed Global Times newspaper said.
China's foreign ministry confirmed that the employee, Simon Cheng, was detained in Shenzhen. Britain has expressed its extreme concern about the case.
U.S. President Donald Trump over the weekend warned against a crackdown in Hong Kong like Beijing's suppression of pro-democracy protests in Tiananmen Square in 1989, which would make reaching a deal he has been seeking to end a trade war with China "very hard". (Reporting by Donny Kwok, Felix Tam and Farah Master; Writing by Farah Master and Nick Macfie; Editing by Robert Birsel and Clarence Fernandez)