Hong Kong leadership candidates have launched a final push for votes, on the eve of the hardest fought election since the city's handover from British rule in 1997.

Leung Chun-ying, a former property consultant, is tipped to win a majority of votes in the electoral college when the 1,200 mainly pro-Beijing delegates meet to choose the regional financial centre's new chief executive on Sunday.

The 57-year-old son of a policeman had secured between 563 and 643 votes as of Friday, the South China Morning Post newspaper reported, after the biggest pro-Beijing party, the Democratic Alliance for the Betterment and Progress of Hong Kong, said they would support him as the city's new leader.

His main rival, former businessman Henry Tang, dismissed reports that he was considering bowing out of the race.

"I will use the rest of my time to continue canvassing for votes," Tang told a news conference, flanked by his wife and sons, while conceding that he is facing an "uphill battle".

"When I announced my candidacy, I had every expectation that it would be a long and treacherous campaign. Indeed it has been," the 59-year-old Tang said.

Hong Kong reverted to Chinese control from British rule 15 years ago, with a semi-autonomous status that guarantees broad social freedoms under limited democracy.

The vast majority of Hong Kong's seven million residents have no right to determine who will replace Donald Tsang, the current chief executive, whose term expires in June, as the southern Chinese city's next leader.

Still, more than 126,000 people cast votes in what was billed as a civil referendum on Saturday, according to public broadcaster RTHK. 

Tsang and his predecessor, Tung Chee-hwa, the city's first post-handover leader, were elected virtually unopposed after receiving the open backing of Beijing.

Tang, heir of a textile fortune, was considered an overwhelmingly favourite for the leadership thanks to his ties to industrialists and bankers, who have run the city in partnership with Beijing since the handover.

But a series of scandals involving his personal life and the discovery of an illegally converted basement at his luxury home have seen his approval ratings plunge and reportedly prompted Beijing to shift support to Leung.

Leung is also an establishment figure but lacks Tang's insider status with the city's business community. He refused to comment on his chances when asked by the local media on Saturday.

Some observers say that both men are regarded as pro-Beijing establishment figures with few ideas for addressing the issues that concern Hong Kong residents, such as the yawning gap between rich and poor and sky-high property prices.