Ukrainian protesters blockaded the main government building in Kiev in an attempt to force President Viktor Yanukovych from office, following his decision to abandon an EU integration pact.
This move follows unrest across the country, where demonstrations at the weekend saw violent clashes with the police, and were attended by as many as 350,000 people.
These demonstrations were the biggest public rally in the ex-Soviet state since the "Orange revolution" nine years ago.
Prime Minister Mykola Azarov accused the opposition of planning to seize the parliament, while Mr Yanukovych appealed for calm, saying protests should be peaceful and law-abiding.
"Any bad peace is better than a good war" Mr Yanukovych said in his first comment on the mass unrest over the weekend, adding that "everyone must observe the laws of our state."
In a sign that he felt the security situation was under control, Mr Yanukovych announced he will be sticking to a plan to travel to China, where he is seeking loans and investment to avert a debt crisis.
His decision to abandon a trade pact with the European Union and instead seek closer economic ties with Russia has stirred deep passions in a country where many people yearn to join the European mainstream and escape Moscow's influence.
The resulting unrest has hammered Ukraine's financial markets, underlining the fragile state of the economy.
Russian president Vladimir Putin has blamed outside actors for the protests, which he said amounted to an attempt to unsettle Ukraine's legitimate rulers.
"This reminds me more of a pogrom than a revolution," Putintold reporters on a visit to Armenia.
However, protesters in the capital remain defiant. "We have no other choice but to defend ourselves and the gains we have made," said Taras Revunets, at Kiev's city hall, which hundreds of demonstrators occupied on Sunday.
With many worried that unrest in the country could endanger their savings, the central bank sought to head off panic withdrawals from the nation’s banks.
In a video statement, its chairman said the bank would not introduce any financial restrictions. "I urge everyone to have confidence in the banking system and maintain their savings," said Ihor Sorkin.
Meanwhile, the White House has said that violence by the Ukrainian government against protesters was unacceptable and urged authorities to respect Ukrainians' rights to freedom of expression and assembly.
"The violence by government authorities against peaceful demonstrators in Kiev on Saturday morning was unacceptable," White House spokesman Jay Carney told reporters at a briefing.
Mr Carney described reports of journalists and members of the media being assaulted and targeted by security forces as "disturbing,"