Both Russian and Ukrainian governments say Moscow and Kyiv have not signed an agreement when the two countries’ presidents met on Friday.
The Kremlin says no deal was agreed on reducing Russian gas prices, and the two leaders did not discuss Ukraine’s possible membership of a customs union.
The unscheduled meeting took place in Russia’s Black Sea resort of Sochi.
Dmitry Peskov, a spokesman for the Russian president, said Vladimir Putin and Ukrainian President Viktor Yanukovych discussed “cooperation in energy”, but that “no final agreement” had been reached.
Arseniy Yatsenyuk, a Ukrainian opposition leader allied to the jailed former prime minister Yulia Tymoshenko, had warned earlier that an accord with Russia would be a “political and economic catastrophe”.
There has been concern in European circles since President Yanukovych pulled Ukraine out of a planned deal with the EU.
A delegation of centre-right members of the European Parliament is visiting Kyiv.
“It looks (like) he is going more and more to Russia, but I do not believe that in Sochi the final decision was taken. At least it was not signed, the custom union,” said Elmar Brok of the centre-right EPP, who is also chairman of the Parliament’s foreign affairs commission. “Therefore we should give all the chances to the Ukrainian people that they can change Yanukovych’s mind and we have to say that the door to Europe is open.”
As anti-government, pro-EU demonstrations continue in Kyiv there are fears of another police clampdown.
“We know that Yanukovych has asked already in 2004 for violence and therefore it might be a possibility, but that would mean that he would run a country like a dictator, that he becomes like an Ukrainian Lukashenko,” Brok added.
Meanwhile special police forces spent the night at the state TV headquarters in Kyiv, saying they needed to ensure security because of protests nearby.
Thousands of pro-EU demonstrators have again been gathering in Independence Square on Saturday.
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