The head of the International Monetary Fund Christine Lagarde said there is no need to "panic" in terms of delivering economic aid to Ukraine.
"We do not see anything that is critical, that is worthy of panic at the moment," she told reporters in Washington. "We would certainly hope that the (Ukrainian) authorities refrain from throwing lots of numbers which are really meaningless until they've been assessed properly."
Ukraine's new leaders say they need $35 billion (£21 billion) over two years to avoid bankruptcy and an EU diplomat said Ukraine had asked for an immediate infusion of $4 billion.
The country's finance minister said he hoped that the IMF would work on an aid package of at least $15 billion.
An IMF team is set to arrive in Kiev early next week to assess the economic situation.
Pro-Russia activists recaptured administrative headquarters in the Ukrainian city of Donetsk and flew the Russian flag from its roof.
ITV News' Europe Correspondent describes the tense atmosphere surrounds a central government building in Donetsk .
New footage obtained by ITV News shows Russian troops firing warning shots as Ukrainian soldiers approached during a tense stand-off today.