The Cross-Harbour Tunnel, which links Hong Kong Island to the rest of the city, had been closed for two weeks after protesters blocked the approach with tons of debris and set the toll booths on fire.

A search of the Hong Kong Polytechnic campus the previous day found just one woman, in weak condition, and a senior university official said it was unlikely anyone else remained.

On Wednesday morning, as Chinese soldiers went through drills nearby the university, Polytechnic officials said a few people might still be hiding in the urban campus, trying to avoid arrest.

Police have cordoned off the area to try to prevent anyone from escaping.

University vice president Alexander Wai, who led a search of the campus by seven teams, said he could not rule out that some people remained, but "the possibility is not very high".

Attention in Hong Kong has shifted to city leader Carrie Lam's response to a major loss in local elections on Sunday, with the results seen as a public rebuke of her tough line on the protests.

The pro-democracy bloc won control of 17 out of 18 district councils in the election, which was seen as a barometer of public support for more than five months of pro-democracy protests.

Lam, after issuing only a written statement on Monday, offered no concessions to anti-government protesters, saying only that she would accelerate dialogue and identify ways to address societal grievances.

She said the central government in Beijing did not blame her for the election setback, and that while it may have reflected unhappiness with the government's handling of the unrest, it also showed many people wanted an end to the violence.

"Let me just stress that after these five-six months, Hong Kong people have realised very clearly that Hong Kong could no longer tolerate this chaotic situation," Ms Lam told reporters after a weekly meeting with advisers.

Her refusal to compromise could spark more unrest at a time when the semi-autonomous Chinese territory has plunged into its first recession in a decade.

The streets around Polytechnic were the scenes of fierce clashes with police 10 days ago, with protesters using the campus as a base, while shutting down access to the Cross-Harbour Tunnel.

The government hopes to take advantage of the current lull in violence to accelerate public dialogue and set up an independent review committee to find solutions to deep-seated societal issues, Lam said.

Beijing is treading cautiously partly to avoid jeopardising trade talks with the United States.

It also faces pressure from planned US legislation that could derail Hong Kong's special trade status and sanction Hong Kong and China officials found to violate human rights.

Australian Associated Press