A Monday deadline for protesters to clear Hong Kong's barricaded streets loomed as the territory's Beijing-backed leader claimed the disorder risked "serious consequences" for public safety.

Chief Executive Leung Chun-ying said late on Saturday that the government was determined to "take all necessary actions to restore social order" and allow residents to "return to their normal work and life".

In particular he pointed to the need to allow government staff to resume work by Monday morning.

Protesters, calling for universal suffrage, have camped out in several commercial districts of the city, blocking roads and access to government offices.

Crowds had thinned out by Sunday afternoon in the downtown Admiralty district near the government headquarters. Hours earlier tens of thousands had turned out there in the biggest gathering yet of the week-long protest.

It remained to be seen whether protesters had heeded Leung's call or merely headed home for some rest before taking to the streets again later at night, which has been the pattern all week.

Principals from universities have called on students and teacher who have been protesting to come back to classes.

Lu, a 24-year-old designer,msaid her parents think she is wasting her time but she will continue to protest.

"I want to make some changes, make Hong Kong a better place. I'm not alone," she told Al Jazeera.

She said she was worried about the future of the protest movement because she, and others, had to go back to work.

But, she added, "the social media campaign is getting stronger and could make the revolution last longer, until we get a satisfactory answer to our demands".

The protesters are demanding the right to nominate who can run as Hong Kong's next leader in 2017 elections.

The Chinese government, which regained sovereignty over Hong Kong from Britain in 1997, insists that only pre-approved candidates will be able to stand and has repeatedly said the protests are doomed to fail.

'Serious consequences'

Leung issued an ominous warning about what would happen if the protests were not ended and streets near the government offices cleared.

"The situation may probably evolve into a state beyond control, and will have serious consequences to public safety and social order," he said.

Fresh clashes broke out on Sunday morning, with riot police using batons and pepper spray to fight back demonstrators.

Sunday marked exactly a week since police fired tear gas on protesters in an effort to disperse them, but only adding sympathy to their cause and boosting numbers.

The latest skirmishes erupted in the commercial district of Mong Kok, away from Admiralty where tens of thousands had gathered for a peace rally, singing democracy anthems.

Tensions flared in Mong Kok as crowds of protesters surrounded police, accusing them of cooperating with gangsters, according to AFP reporters at the scene. Police responded with pepper spray.

The district was also the site of ugly scenes on Friday, as protesters were physically attacked. The violence led to accusations that the police failed to protect the demonstrators from the opposing crowds and speculation authorities had hired paid thugs to break up the protests.

Al Jazeera's Divya Gopalan, reporting from Admiralty, said student leaders emphasised the need for the protest movement to remain peaceful and "not give the government any reason to break it up".

Mervyn, a 28-year-old sea-farer who came from Singapore to support the protests, said Hong Kongers had seen popular uprisings elsewhere in the world turn violent and were determined to keep protests peaceful.

"They watched the Arab Spring unfold. We are a peace-loving crowd here - we don't want the violence seen elsewhere."

He told Al Jazeera that the demonstrations had reached a stalemate, but the demonstrators were "not going to budge".

"We'll see who tires first!"