Thousands of democracy protesters have defied tear gas and police baton charges to remain on the streets of Hong Kong amid rising international tensions.
Some demonstrators wore masks and resorted to umbrellas or plastic capes to protect themselves - prompting the phrase "umbrella revolution" to trend on social media.
The UK Foreign Office said it was "concerned" by the heavy response to the protests in its former colony - but China warned the international community not to "interfere".
Chinese Foreign Ministry spokesman Hua Chunying said: "Hong Kong is China's Hong Kong. Hong Kong is purely our internal affair.
"We are resolutely opposed to any foreign country using any method to interfere in China's internal affairs."
Protesters remained defiant on Monday night
Some wore plastic and goggles, fearing more tear gas
The Hong Kong government said it had pulled out riot police on Monday as the protests began to calm.
A spokesman called on the activists to leave the protest areas peacefully - but many remain camped on a normally busy highway near the government headquarters.
Hong Kong's chief executive should resign, say demonstrators
Organisers estimate as many as 80,000 people have taken to the streets since Friday.
Police fired 87 rounds of tear gas on Sunday after being charged by "violent protesters", and said 41 people had been injured, 12 of them police officers.
Demonstrator Rick Chan said: "I came last night and saw police fire many rounds of tear gas at the crowd, who were mostly young students and even included some old people."
Protesters flee the tear gas on Sunday night
Police lined up against the demonstrators
Photo-sharing site Instagram has also reportedly been blocked in China, suggesting authorities could be worried about inspiring similar protests on the mainland.
Many photos of the demo have been hashtagged "Occupy Central".
The phrase was blocked on Sunday on Weibo, China's version of Twitter.
A movement to occupy central Hong Kong, in protest at Chinese interference, was originally planned for National Day on Wednesday, but began early on the back of separate student protests.
Thousands remained on the streets on Monday
Last month, the Communist Party ruled that while Hong Kongers could choose their next leader or chief executive in 2017, they must select from candidates picked by Beijing who must declare their "love" for China and its Communist system.
Under the agreement of the 1997 handover from Britain to China, Hong Kong was allowed to have an independent legal and political framework.
Unlike mainland China, protests are allowed - but the current demonstrations are one of the biggest political challenges to Beijing since the Tiananmen Square crackdown 25 years ago.
"The British government is concerned about the situation in Hong Kong and is monitoring events carefully," said a UK Foreign Office spokesman.
Phones were raised aloft outside the Hong Kong government complex
Protesters have been blocking the main street to the financial district
"It is Britain's longstanding position, as a co-signatory of the Sino-British Joint Declaration, that Hong Kong's prosperity and security are underpinned by its fundamental rights and freedoms, including the right to demonstrate."
Occupy Central co-organiser Dr Chan Kin-man urged "fearless" protesters to remain on the streets until their calls were heeded.
In a statement, the group called on Hong Kong's Chief Executive, Leung Chun-ying, to resign, saying his "non-response to the people's demands has driven Hong Kong into a crisis of disorder".
The protests have affected Hong Kong's commercial hub, forcing bus routes to be cancelled or diverted and banks to close.
Clashes also broke out in Taiwan when dozens of students gathered in the lobby of the Hong Kong Trade Office in Taipei in support of the democracy protests.