Ukraine's President Viktor Yanukovych and his Russian counterpart Vladimir Putin have held surprise talks on a "strategic partnership treaty," BBC News reported.

Yanukovych flew from China to Sochi in southern Russia for the meeting. He has also cancelled a visit to Malta. Last month he shelved a partnership deal with the EU, triggering angry protests in Ukraine's capital Kiev.

In Sochi he discussed "preparation of a future treaty on strategic partnership" with Russia, his press service said. The talks covered various economic issues, the statement said, without elaborating.

Thousands of anti-Yanukovych protesters remain outside the government building on Kiev's Independence Square, braving bitter cold. They are furious that he made an 11th-hour U-turn in relations with the EU, refusing to sign an association agreement that had been prepared during years of negotiations.

Putin has been urging Ukraine to join Russia's customs union with Belarus and Kazakhstan - a union whose entry terms are far less demanding than the EU's.

In recent months Russia has put Ukraine under economic pressure, imposing long customs delays at the border and banning imports of Ukrainian sweets.