Pro-European protesters take cover behind a burnt bus during clashes with riot police in Kiev January 22, 2014. [Photo/Agencies]

KIEV - Ukraine's prime minister said on Wednesday that anti-government protests had brought "terrorists" onto the streets of Kiev and pledged to punish all "criminal action", even as protesters confronted police near government headquarters.

Prime Minister Mykola Azarov, speaking to his cabinet, took a tough line on the protesters, who on Wednesday massed anew in their hundreds, inflamed by reports of at least three demonstrators dying overnight - two of them from gunshot wounds.

In words that appeared to foreshadow a police crackdown, Azarov said: "Terrorists from the 'Maidan' (Independence Square) seized dozens of people and beat them. I am officially stating that these are criminals who must answer for their action."

Azarov accused opposition leaders of inciting "criminal action" by calling for anti-government protests, which he said destabilised the situation in Ukraine, a large former Soviet republic of 46 million people.

But in a move underlining US criticism of his government's heavy-handed treatment of the protesters, the US embassy in Kiev said it had revoked the visas of several Ukrainians linked to police violence against protesters in November and December.

It did not name the officials but said it was considering further action against those responsible for the current violence.

The European Union called on Ukraine's government and opposition to "engage in a genuine dialogue".

"I strongly condemn the violent escalation of events in Kiev overnight leading to casualties. The reported deaths of several protesters are a source of extreme worry," EU foreign policy chief Catherine Ashton said in a statement.

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