Both sides in Ukraine are claiming the right to form a new government after what is shaping up to be a close parliamentary election.
With more than 90 percent of the votes counted, Prime Minister Viktor Yanukovych's pro-Russian Party of Regions has 34 percent of the vote.
Opposition leader Yulia Tymoshenko and her pro-reformist bloc has 31 percent and President Viktor Yushchenko's Our Ukraine Party trails with 14 percent.
Mr. Yanukovych says the results give him the right to form a new government. But Tymoshenko says she will ask President Yushchenko to let her put together a new cabinet. They plan to form a coalition that Tymoshenko says will give them more parliamentary seats than Mr. Yanukovych.
International election observers said Sunday's voting was open and competitive and conducted mostly in line with international democratic standards.
But President Yushchenko said Monday he is concerned about reported delays in vote counting in eastern and southern regions of the country, where support for Mr. Yanukovych is strong. He raised the possibility of fraud and ordered an immediate investigation into the problems.
Mr. Yushchenko and Ms. Tymoshenko were political allies in Ukraine's "Orange Revolution" - the mass protests against the results of the 2004 presidential election that declared Mr. Yanukovych the winner. Mr. Yushchenko won the re-vote and named Ms. Tymoshenko prime minister. He later fired her.
President Yushchenko called for Sunday's early elections in April, after dissolving parliament. He accused Mr. Yanukovych of illegally courting members of the president's party to strengthen the prime minister's support in parliament.
Some information for this report was provided by AP.
