Former government adviser and property consultant Leung Chun-ying won Hong Kong's leadership election on Sunday, according to official results.

Leung, 57, will replace outgoing chief executive Donald Tsang in June after winning 689 of the votes from the 1,200-strong election committee that chooses the southern Chinese city's leader.

Applause broke out from delegates on the floor of the tally room as his count ticked past the 601 minimum required for victory.

His main rival, Henry Tang, finished with 285 and pro-democracy candidate Albert Ho on 76, an official said.

Thousands of protesters gathered outside the harborside convention centre where the vote took place, demanding full democracy in the semi-autonomous former British colony, which returned to Chinese rule in 1997.

The protests, which could be heard inside the tally room, were noisy but generally peaceful.

Leung, whose humble origins as a policemen's son stand in stark contrast to Tang's background as heir to a textile fortune, told reporters earlier that he wanted the broadest possible community support.

"Every resident has their own view about the election. I will try my best to get rid of people's negative perception about this election," he said. (AFP)