Hundreds of Hong Kong pro-democracy activists rallied Friday outside the British Consulate, urging the city's former colonial ruler to emulate the U.S. and take concrete actions to support their cause, as police ended a blockade of a university campus after 12 days.

Waving British flags, the activists urged Britain to ensure that Hong Kong political dissidents do not suffer the same fate as Simon Cheng, a former British Consulate employee in the city who says he was detained and tortured by Chinese secret police.

The rally came a day after U.S. President Donald Trump signed into law two bills to support democracy and human rights in the semi-autonomous Chinese territory.

"The U.K. should enforce similar laws and should have done even more" to support the protest movement, said a masked rally organizer who identified herself only as Dawn. Activists handed a petition to a consulate official before leaving.

Beijing denies torturing Cheng and says he was held for soliciting prostitution during a business trip to mainland China in August. Cheng says he agreed to confess to avoid harsher charges. He says he was hooded, beaten and chained to a metal frame as Chinese secret police sought information on activists involved in the protests and on Britain's purported role.

Cheng has left the consulate and is in hiding.

Violence in Asia's top financial hub has abated since a stunning victory by the pro-democracy camp in Nov. 24 local elections, seen as a sharp rebuke to the city's embattled leader, Carrie Lam.

Protesters are planning more rallies this weekend to keep up their pressure on Lam, who has refused to offer any new concessions to their demands, including greater democracy and an independent probe into alleged police brutality.

At a lunchtime rally Friday, hundreds of people chanted slogans and carried posters telling Lam that "it's time to step down." Protesters disrupted traffic in at least two places but dispersed after police issued warnings.

University cleanup could take months: official

On Thursday night, thousands joined a large rally to thank the U.S., on its Thanksgiving Day holiday, and to call on other countries to join the U.S. in supporting the protest movement, now in its sixth month.

One of the new U.S. laws prescribes sanctions on officials found guilty of human rights abuses and requires an annual review of a special trade status for Hong Kong. The other bans the export of certain non-lethal munitions to Hong Kong police.

China has warned of strong countermeasures and Hong Kong's government has slammed the U.S. move as meddling in its affairs.

During an official visit to Thailand, Lam said Hong Kong's fundamentals, including its "one country, two systems" framework, remain strong despite the unrest.

"I and my government are listening to our people with a view to resolving some deep-seated problems in Hong Kong through dialogue," she said, adding that "Hong Kong can bounce back."

A police officer gathers forensic evidence at the campus of the Polytechnic University in Hong Kong. (Thomas Peters/Reuters)

Earlier Friday, police lifted their siege of Polytechnic University, a key earlier battleground with pitched battles between protesters and riot officers.

Police said they seized 3,989 gasoline bombs, 1,339 explosive items, 601 bottles of corrosive liquids and 573 weapons over two days of searching. No protesters were found inside. Some 1,100 people have already left or have been arrested by police.

A university official estimated it would take five to six months to repair the extensive damage to the campus.

Separately, police said two high school students were detained Wednesday for possessing TATP, or tri-acetone triperoxide powder, a powerful explosive that has been used in bomb attacks worldwide. Police said it was alarming that such dangerous explosives were found with young students.

The unrest began in June with a huge march against an extradition bill that was seen as an erosion of freedoms promised when Hong Kong returned to Chinese control in 1997. The movement has since expanded into a protest against growing Chinese interference in the city. Police say 5,890 people have been arrested since the unrest started.