A pro-democracy candidate won a Hong Kong weekend by-election while a rival from a radical pro-independence group arrested on riot charges placed a surprising third in a vote seen as a measure of political tension in the Chinese city.

The mainstream Civic Party's Alvin Yeung won the Legislative Council seat with 160,880 votes representing 37 percent of the turnout, edging out pro-Beijing candidate Holden Chow by about 10,000 votes, according to results released early Monday.

But the front-runners were overshadowed by Edward Leung of Hong Kong Indigenous, who garnered 15 percent of about 434,000 votes cast Sunday. Leung is one of the leaders of the group, which is part of a fledgling movement advocating Hong Kong's independence from China.

The movement has gained support amid growing unease over signs Beijing is tightening its grip on the specially administered Chinese region, which is promised civil liberties unseen on the mainland under the "one-country, two-systems" principle that took effect when Britain ceded control to China in 1997.

Hong Kong Indigenous is one of a number of groups formed after pro-democracy street protests in 2014 ended without a satisfactory resolution after Beijing refused to give any major concessions.

"There's a certain amount of Hong Kong people who support our political belief and means of fighting" for democracy, Leung told reporters. The group advocates radical protest methods. "It has given us more power to fight against the authorities."

Leung is among dozens of people charged with taking part in a riot following a violent nightlong clash with police at a Lunar New Year holiday street food market earlier this month that was sparked by concerns that the city's local culture is disappearing.

Beijing has condemned groups like Leung's, calling them "radical splitting forces."

Hong Kong Financial Secretary John Tsang warned last week that rising political tensions are threatening the city's economic growth.

Sunday's vote is seen as a prelude to citywide elections later this year that are expected to be fiercely contested by pro-democracy and pro-Beijing parties.