A European mediator flew into Kiev to meet with the Ukrainian government and opposition on Wednesday, but there was no sign of an end to the standoff that has paralysed the centre of the city and the work of the government for days.

Thorbjorn Jagland, secretary general of the Council of Europe, was sober about the possibility of progress after meeting with Prime Minister Mykola Azarov, and said he had impressed upon the Ukrainian authorities the need to launch an independent investigation into police violence against peaceful protesters over the weekend.

"It's important to have an investigation into this that everyone can trust," said Jagland, adding that he hoped to facilitate dialogue between the government and opposition parties. "I don't know whether it is possible to have this dialogue," he admitted.

Azarov, who was carried through an emotional no-confidence vote in parliament on Tuesday by the support of President Viktor Yanukovych's Party of Regions, criticised the protest movement during a cabinet meeting on Wednesday.

"We must decide all this in a calm environment," he said. "Not in the streets, but in a responsible dialogue." However, opposition politicians, including heavyweight boxer Vitali Klitschko, have called for the government to resign and for snap presidential elections. They say they will continue to blockade government buildings until their demands are met.

Demonstrations began after Yanukovych backed away from a trade deal with the EU, citing the importance of ties with Russia. The unrest appeared to be dying down, until riot police cleared Independence square of protesters on Saturday, in violent scenes which provoked a mass protest on Sunday.

The square, hub of the 2004 Orange Revolution, remains barricaded and filled with protesters, and the three main opposition parties insist that there can be no negotiations until Yanukovych calls snap elections. Yanukovych himself has left the country for a long-planned visit to China, where he took time out to view the terracotta army on Wednesday, apparently unconcerned by events at home.

"The big question is whether the opposition can keep people coming to the square, and keep the pressure on, or whether people will get bored," said political analyst Volodymyr Fesenko. "The next week will show us who the winner is."

Russia and the west have accused each other of meddling in Ukraine's internal affairs, with the EU furious that the trade deal, years in the making, was scuppered after apparent pressure from Moscow.

Meanwhile Russian foreign minister Sergei Lavrov, on a visit to Brussels, lashed out at Nato for its criticism of the Ukrainian authorities' violent response to protests. "I don't understand why Nato adopts such statements," said Lavrov. "I hope that Ukrainian politicians will be able to bring the situation into a peaceful vein. We encourage everybody not to interfere."