(Bloomberg) -- Clouds of tear gas returned to Hong Kong over the weekend as police and protesters clashed, signaling pro-democracy rallies are set to drag on after demonstrators got a boost from an election win and support from the U.S. Congress.Tensions rose in the former British colony -- a special administrative region of China since 1997 -- as thousands of black-clad protesters marched in the busy tourist district of Tsim Sha Tsui on Sunday afternoon. Unrest had been brewing since late Saturday, when a group blocked roads and set fire to a subway station entrance.The violence took a pause with the elections a week earlier, as Hong Kong residents handed an overwhelming victory to pro-democracy candidates in a vote for local district councils on Nov. 24. While the officials they elected represent what's considered as the lowest rung of the government, the win was a stunning repudiation of the city's Beijing-backed government. Hong Kong leader Carrie Lam didn't make any new concessions to protesters after the poll, a move that could have fueled the anger seen over the weekend.At the Tsim Sha Tsui event, police said smoke grenades were hurled by what it labeled 'rioters' to cause fear and panic among demonstrators, prompting law enforcement action that included tear gas to disperse the crowd. Bricks were thrown at police officers in the area, as well as in nearby Whampoa, where shops were also vandalized. One passerby was attacked, police said.Earlier in the day, people carrying U.S. flags and banners marched to the U.S. consulate in a peaceful rally to express gratitude after President Donald Trump signed legislation last week in support of the demonstrators. While the crowds have dispersed Sunday night, scores of police officers in riot gear were still seen lining the streets as of 2 a.m. on Monday.MTR Corp., the city's subway operator, said it expects rail and bus services to resume normally on Monday, with the possibility that some stations and rail sections may close early, especially on weekends. The University station on the East Rail line will remain shut for repairs, and entrances and exits to some stops that had excessive damage from the protests will also not be accessible.Subway stations and even tracks were vandalized during the protests in the past few months, with MTR's crews rushing through repairs. The stock -- once one of Hong Kong's safest stock bets -- has lost more than a fifth of its value since its peak this year in July, making it the second-worst performer on Hong Kong's benchmark Hang Seng Index. The stock is poised to recover quickly when the city's situation eventually settles, according to Goldman Sachs Group Inc. analysts, who've upgraded MTR to buy from neutral.Police ConductMeanwhile, China said it 'strongly' opposed an opinion piece by United Nations High Commissioner for Human Rights Michelle Bachelet in the South China Morning Post on Saturday, accusing her of meddling in the country's affairs and emboldening Hong Kong protesters to commit violence.Bachelet urged the city's government to conduct a 'proper independent and impartial judge-led investigation' into reports of excessive use of force by police. She also called on Lam's administration to 'prioritize a long-overdue process' of meaningful and inclusive dialogue with the people of Hong Kong.Hong Kong's newly appointed police chief, Chris Tang, said an independent probe into the use of force by police would be unjust, the South China Morning Post reported Sunday, citing comments he made in a radio program.China has also arrested two overseas nationals for their alleged involvement in Hong Kong's protest movement, state newspaper Southern Daily reported, citing information from the national security agency. Taiwanese Lee Meng-chu and Lee Henley Hu Xiang of Belize were arrested by the national security authorities in the southern Guangdong province, the local paper said in two reports published Saturday.(Updates with clashes in fourth paragraph, subway plans for Monday in sixth.)To contact the reporter on this story: Manuel Baigorri in Hong Kong at email@example.comTo contact the editors responsible for this story: Brendan Scott at firstname.lastname@example.org, Linus Chua, Tony CzuczkaFor more articles like this, please visit us at bloomberg.com2019 Bloomberg L.P. Click here to read full news..