Thousands of protesters forced the temporary closure of the Hong Kong government's headquarters on Monday after they clashed with police outside, defying orders to retreat.
Chaos erupted as commuters made their way to work, with hundreds of protesters surrounding Admiralty Center, which houses offices and retail outlets, in a tense stand-off with police. The central government offices and the legislature were forced to close in the morning, as were scores of shops, according to Reuters.
Police said at least 40 arrests were made.
Hong Kong Chief Executive Leung Chun-ying said police had been very tolerant but would now take "resolute action".
"Some people have mistaken the police's tolerance for weakness," he told reporters.
"I call for students who are planning to return to the occupation sites tonight not to do so," said Leung, who did not respond when if police would clear the sites on Monday night.
The overnight clashes came after student leaders called on activists to escalate their protests and surround government headquarters
The protesters are demanding free elections for the city's next leader in 2017 rather than the vote between pre-screened candidates that Beijing has said it would allow.
The Hong Kong rallies drew more than 100,000 on to the streets at their peak after they began two months ago. Numbers have since dwindled and public support for the movement has waned.
