The protesters had been due to leave the area within hours
Security forces in Sri Lanka have raided the main anti-government protest camp in the capital Colombo and have begun pulling down tents.
Hundreds of troops and police commandos moved on the protesters outside the presidential offices, hours before they were due to leave the area.
A BBC video journalist was beaten by the army and one soldier snatched his phone and deleted videos.
It comes after Ranil Wickremesinghe was sworn in as president.
Sri Lanka's ex-president Gotabaya Rajapaksa fled the country last week.
Mr Wickremesinghe - the former prime minister - is seen as deeply unpopular with the public, and has vowed tough action against demonstrators. But some protesters have said they will give him a chance.
Sri Lanka has seen months of mass unrest over an economic crisis.
Many blame the Rajapaksa administration for mishandling the nation's finances, and see Mr Wickremesinghe as part of the problem. But there were few demonstrations on the streets the day after he won the parliament vote.
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Soon after Mr Wickremesinghe was sworn in, he made clear that any attempt to topple the government or occupy government buildings was not democracy and warned that those who indulge in such activities will be dealt with firmly according to the law.
There had been concerns among demonstrators that the government might gradually crack down on the protest movement sooner or later.
Troops descended on the camp in the early hours of Friday morning, pulling down tents and breaking protesters' property. They then pushed the demonstrators - who were due to leave within hours - behind a barricade.
One BBC video journalist was beaten while another had a mic snatched and thrown away.
The government is yet to comment.