Hong Kong Chief Executive CY Leung has warned pro-democracy activists not to return to the streets following the latest outbreak of violence.
His comments come after some of the worst clashes between protesters and police since the pro-democracy demonstrations began two months ago.
Police armed with pepper spray, batons and water hoses cleared activists from Lung Wo Road in the Admiralty district.
Government offices were briefly shut on Monday.
In another development, prominent student leader Joshua Wong announced on Monday that he and two others were beginning a hunger strike to demand renewed talks with the Hong Kong government.
“Living in these troubled times, there is a duty. Today we are willing to pay the price,” the students said in a statement.
Student leaders opened talks with government negotiators in October but they failed to achieve an agreement and discussions have not been resumed.
Earlier, in a move which prompted fears of further violence, an injunction was granted to clear an area just west of the main protest site in Admiralty.
“From this day on, the police will take resolute action when carrying out their duties. I call on the students who are thinking of returning to the occupation area tonight not to do so,” Mr Leung said.
“Don’t mistake the police tolerance as weakness.”
Protesters want the people of Hong Kong to be allowed to choose their leaders in the 2017 elections without intervention from Beijing.
The Chinese government has said it will allow direct elections, but candidates for the post of chief executive will be screened first.
The unrest flared late on Sunday, after student protest leaders called on supporters to converge on the offices of Mr Leung on Lung Wo Road.
The road is a short distance away from Connaught Road in Admiralty, the major road protesters have been occupying for two months.
The court injunction calls for the dismantling of barricades in part of Connaught Road and Harcourt Road, just west of the main Admiralty protest camp.
Protesters, many wearing hard hats and carrying umbrellas – the symbol of their movement – moved into Lung Wo Road on Sunday, throwing bottles, helmets and umbrellas towards police.
Police ordered them to retreat, then charged at protesters, eventually forcing them out of the area. Police said that 40 people were arrested and a number of officers were injured.
On Monday morning government offices were shut and staff were told to stay at home, but government employees were back at work by the afternoon.
Last week, police dismantled one of the three major protest camps in the Mong Kok commercial district and made 100 arrests.
China has meanwhile hit back at criticism of its decision to bar a UK parliamentary committee from entering Hong Kong, a former British colony.
Foreign ministry spokeswoman Hua Chunying said Beijing had made clear to the UK government many times that it opposed “the so-called delegation of the British parliament’s foreign affairs committee going to Hong Kong for a so-called investigation”.
She described the MPs’ move as “overt confrontation” in a riposte to the committee’s chairman, Sir Richard Ottaway, who accused China on Sunday of acting in an “overtly confrontational manner”.