Hong Kong's embattled leader defiantly rejected demands to resign and sent his deputy to talk to pro-democracy demonstrators, as huge crowds rallied outside his government's besieged headquarters early Friday for a fifth consecutive night.

Huge throngs who have shut down central areas of the city with mass sit-ins all week had set a midnight deadline for Chief Executive Leung Chun-ying to step down and for Beijing guarantee the former British colony full democracy.

The Dalai Lama said he was praying Thursday for a peaceful resolution to the stand-off between pro-democracy demonstrators and security forces in Hong Kong but said the outcome was "very difficult" to predict.

The Tibetan spiritual leader, who has lived in exile ever since Chinese forces crushed a failed uprising in his homeland in 1959, told Agence France-Presse he was closely watching the situation unfolding in downtown Hong Kong.

Hong Kong pro-democracy protesters demanded the city's embattled leader heed their ultimatum to resign Thursday, but China backed him "firmly and unshakably" and pledged support for the police.

Demonstrators, who have shut down central areas of the southern Chinese city with a mass sit-in, have given Chief Executive Leung Chun-ying until midnight to step down, or face escalated action.

Tensions in Hong Kong soared Thursday after police were seen unloading boxes of tear gas and rubber bullets close to the city's besieged government headquarters as the authorities urged pro-democracy demonstrators to disperse "as soon as possible".

Protesters have shut down central areas of the southern Chinese city with a mass sit-in, including outside the city's legislative assembly, and have given Chief Executive Leung Chun-ying until midnight to step down, or face escalated action.

China Wednesday scolded the United States saying pro-democracy protests sweeping Hong Kong were none of its business and brushing off U.S. calls for restraint warning it will not tolerate "illegal acts."

"The Chinese government has very firmly and clearly stated its position. Hong Kong affairs are China's internal affairs," Chinese Foreign Minister Wang Yi told U.S. Secretary of State John Kerry ahead of talks at the State Department.

Thousands of slogan-chanting Taiwan residents rallied late Wednesday to support the growing pro-democracy demonstrations in Hong Kong, with one saying the city faces a "life-and-death" moment.

The crowd, many of them Hong Kong students studying in Taiwan universities, raised their fists and sang "Boundless Oceans, Vast Skies", a song by the 1980s Hong Kong band Beyond which has become a theme tune of the protests.

Fearful of comparisons to the 1989 Tiananmen Square crackdown, Beijing has launched a dual effort to suppress news of swelling pro-democracy protests in Hong Kong while giving a heavy spin to what information it allows to get through, analysts say.

Scenes of the massive, yet peaceful, protests that have taken over the streets of the former British colony are being flashed around the world, where the reaction has been mostly supportive.

Thousands of Hong Kong pro-democracy demonstrators massed outside the offices of the city's embattled leader early Thursday in a tense standoff with police, with calls growing for him to resign as mass protests grip the city.

Around 200 police equipped with riot helmets, gas masks and shields stood firm behind metal barricades as more than 3,000 protesters gathered outside Leung Chun-ying's office in the early hours, with some saying they wanted to storm the building, an Agence France-Presse reporter at the scene said.

With well-stocked food stands, fastidious recycling, unmanned phone-charging stations and even a chamber ensemble, Hong Kong's huge protests have a distinctly civilized flavor -- part of a charm offensive to maintain mainstream support.

The city is known for its low crime rate and orderly queues. So it is perhaps not surprising that the protests bringing parts of the Asian financial hub to a standstill -- and the political system to an impasse -- reflect its character.

Hong Kong demonstrators rejected demands immediately to end rallies that have paralyzed the city's downtown, their numbers swelling for a third night before a national holiday Wednesday expected to put their campaign for free elections into overdrive.

Protest leaders are confident of mustering massive crowds, angered at Beijing's refusal to grant full democracy, overnight and into Wednesday for the National Day public holiday marking the 65th anniversary of the founding of Communist China.