Ukraine's prime minister on Monday compared pro-EU demonstrations in the country to a coup, branding them illegal and "out of control".

Tens of thousands have been protesting in Kiev, occupying City Hall and blocking entrances to the government headquarters, in an ongoing standoff after the government failed to sign a key EU pact.

Inside the Kiev mayor's office on Monday, a group of protesters prepared food, while doctors treated the wounded and several young activists lay sprawled asleep on the floor.

The words "Revolution headquarters" have been spray-painted in black across the building, one of several in the center of the Ukraine capital that have been taken over by protesters.

Russian strongman Vladimir Putin on Monday slammed street protests in Ukraine against the government's decision not to sign a key agreement with the European Union and seek closer ties with the Kremlin.

"The events in Ukraine seem more like a pogrom than a revolution," Putin said during a visit to Armenia.

The leaders of France and Poland on Monday condemned violence in Ukraine and called for dialogue between the government and pro-EU demonstrators, the French presidency said.

French President Francois Hollande discussed the crisis with Polish Prime Minister Donald Tusk by telephone, a statement from Hollande's office said.

The EU called for calm in Ukraine Monday and urged authorities to show restraint after a weekend of violent clashes between police and thousands of pro-democracy protesters furious at Kiev's rejection of an EU pact.

Separately, President Viktor Yanukovych telephoned European Commission head Jose Manuel Barroso to ask that Brussels receive a Ukraine delegation to discuss "some aspects" of the pact and an associated free trade deal.

Russian strongman Vladimir Putin on Monday pledged to maintain the Kremlin's influence in the South Caucasus on a trip to Armenia as hundreds of demonstrators protested a decision to join a Moscow-led customs union.

"Russia is not preparing to leave the South Causcasus. On the contrary, we intend to strengthen our presence here," Putin said in televised remarks from the town of Gyumri, where he was expected to visit a Russian military base.

Ukrainian protesters launched a nationwide strike and began to blockade government buildings Monday after violent clashes in which more than 100,000 sought early elections over the authorities' rejection of a historic EU pact.

About 10,0000 supporters of the ex-Soviet state's closer alliance with the European Union and disavowal of old master Russia camped out overnight into Monday on Kiev's iconic Independence Square.

Dozens of police and protesters were injured Sunday in violent clashes that broke out as 100,000 outraged Ukrainians swarmed Kiev in a call for early elections meant to punish authorities for rejecting a historic EU pact.

The crowd chanted "Revolution!" and "Down with the gang" as it drove dozens of helmeted police off Kiev's iconic Independence Square. Protesters also steered a bulldozer within striking distance of police barricades protecting the nearby presidential administration office.

Germany's foreign minister called on Ukraine Sunday to protect peaceful demonstrators and ensure the people's right to assembly, as pro-EU Ukrainians vowed to defy a protest ban.

"I vigorously call on the Ukrainian government to ensure freedom of assembly and to protect the peaceful demonstrators from any kind of intimidation and violence," Guido Westerwelle said in a statement.

Ukrainian President Viktor Yanukovych on Saturday condemned the use of force against an opposition rally at which several dozen demonstrators were wounded.

"I am deeply outraged by events that took place on Independence Square overnight," Yanukovych said in a statement. "I condemn the actions which led to a confrontation and people suffering," he said, vowing that those responsible for the use of force would be punished.