Thousands of police have moved on a large protest camp in the centre of the Ukrainian capital, Kiev.
Police have torn down barricades close to the main opposition site on Independence Square.
A stand-off developed after clashes broke out between security forces and protesters.
The government's decision to withdraw from a free-trade deal with the EU last month has sparked huge street rallies by the opposition.
Sea of police
The latest police action comes after EU foreign policy chief Catherine Ashton held talks with President Viktor Yanukovych on Monday. She was cheered by crowds when she visited Kiev's main protest site.
Riot police and interior ministry officers dismantled some outer barriers but met resistance from opposition supporters.
There are unconfirmed reports that police have begun storming the Kiev city hall, seized by protesters just over a week ago.
