At least 200 000 pro-EU protesters have gathered so far and others continue flocking to downtown Kiev to rally against the Ukrainian government.

The opposition called for mass demonstrations in the Ukrainian capital, starting at noon Sunday.

Thousands of pro-EU protesters remained overnight in Independence Square in the heart of the city. Barricades around the protesters' stronghold have been reinforced with old tires and metal pipes packed with ice and snow following an attempt by special police Berkut to dismantle them earlier this week.

Opposition leaders urge protesters to keep rallying, but also to remain vigilant, fearing "provocateurs" could trigger clashes between rival demonstrators.

In a tragic incident, one man has died of a heart attack during Sunday's protest. An on-site medical team has arrived and has taken the man in an ambulance, but he has passed away on the way to hospital.

Several days ago, another man died at Independence Square during the protests. According to doctors, the cause of death was tuberculosis.

Protests began in November after Ukrainian President Viktor Yanukovych made a last-minute U-turn on a landmark deal with the EU.

Yanukovych has said he fears the association agreement will put at risk many enterprises dependent on trade with Russia.

The president - who claims he eventually will sign the deal - has also admitted being under heavy pressure from Moscow, which wants Kiev to join a Russian-led customs union instead.

Meanwhile, also on Sunday, the European Union said it was discontinuing work on the signing of the association and trade agreement with Ukraine.

European Commissioner on Enlargement Stefan Fule wrote on Twitter that he has told Ukraine's First Deputy Prime Minister Serhiy Arbuzov last week that further negotiations on the agreement would be determined by a clear commitment from Kiev to sign it. As no reply was received by the Ukrainian government, the work under the Agreement is terminated, bTV reported, citing Reuters.

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