(Adds details of clashes, most protesters heading home)
* Protesters clash with police at site of July mob attack
* Demonstrators question lack of prosecutions
* Faceoff stops short of full pitched battles
* China detains British consulate staffer
By James Pomfret and Greg Torode
HONG KONG, Aug 21 (Reuters) - Thousands of Hong Kong residents held a sometimes scrappy anti-government protest on Wednesday at a suburban subway station that was attacked by a mob last month, angry that nobody has yet been prosecuted for the violence.
Some masked protesters clashed with police, spraying fire extinguishers from the inside of Yuen Long station as others smeared the floor with cooking oil, beer and detergent to stop the police advancing.
Some blocked station exits with bins, booths and other station furniture as others sealed roads outside the station, aiming green laser beams at the lines of shield-bearing officers. Others threw empty fire extinguishers at police lines.
Many inside the station sat quietly.
It was the latest in a series of demonstrations since June against a perceived erosion of freedoms in the former British colony that returned to Chinese rule in 1997.
It also marked a return to aggression after a brief lull in tensions following a huge peaceful march on Sunday.
But the standoff stopped short of full pitched battles with police refraining from using tear gas or attempting to storm protester lines. Only one rock was seen hitting a police shield and most protesters were headed home before midnight.
The protest marked the night of July 21, when more than 100 white-shirted men stormed the Yuen Long station hours after protesters had marched through central Hong Kong and defaced China's Liaison Office - the main symbol of Beijing's authority.
Using pipes and clubs, the men attacked black-clad protesters returning from Hong Kong island as well as passers-by and journalists, wounding 45 people.
Democratic Party legislator Lam Cheuk-ting, wounded in the attack by suspected triad gangsters, said he believed the protesters wanted a peaceful night on Wednesday but he could not rule out further violence - from gangsters or the police.
“It is impossible to predict... It is deeply disappointing that all these weeks later we still don’t have an independent inquiry into those events,” he told Reuters.
SHARP REACTION FROM CHINA
Squads of police were stationed on the station perimeter and some protesters jeered and shone lasers at them. A small crowd of masked young men gathered on a station balcony, swearing and cursing at police vans down a side street.
Anger erupted in June over a now-suspended bill that would allow criminal suspects in Hong Kong to be extradited to mainland China for trial. Hong Kong leader Carrie Lam said again on Tuesday the legislation was dead.
The unrest has been fuelled by broader worries about the erosion of freedoms guaranteed under the "one country, two systems" formula adopted after Hong Kong's return to China, including an independent judiciary and the right to protest. Demonstrations have included the storming of the legislature and havoc at the airport.
Beijing has reacted sharply to the protests and has accused foreign countries, including the United States, of fomenting unrest. China has also sent clear warning that forceful intervention is possible, with paramilitary forces holding drills in neighbouring Shenzhen.
U.S. Secretary of State Mike Pompeo reiterated Washington's calls for China to honour its commitment to "one country, two systems".
Speaking to CBS programme "This Morning" on Tuesday, Pompeo highlighted remarks by President Donald Trump at the weekend warning against a crackdown like Beijing's suppression of pro-democracy protests in Tiananmen Square in 1989.
Trump said this would make reaching a deal he has been seeking to end a trade war with China "very hard".
In an editorial on Tuesday, China’s influential state-run tabloid, the Global Times, called Monday's comments by U.S. Vice President Mike Pence linking the trade talks to the Hong Kong protests "outrageous".
Likely worsening already strained ties between Beijing and London, a Chinese national working at Britain's Hong Kong consulate has been detained in China's border city of Shenzhen for violating the law.
Some Hong Kong companies have been dragged into controversy amid the protests.
Pilots and cabin crew at Cathay Pacific Airways described a "white terror" of political denunciations, sackings and phone searches by Chinese aviation officials. (Additional reporting by Felix Tam Writing by Nick Macfie Editing by Frances Kerry)