Talks on offer as Donetsk targeted
Ukraine's new president-elect has promised to negotiate an end to a pro-Russia insurgency in the east, saying he was willing to begin talks with Moscow.
But the Kiev government also launched an air strike on militants who occupied a major airport.
Russia quickly welcomed Petro Poroshenko's offer for talks, raising hopes that his election will indeed ease the protracted crisis that has fuelled tensions unseen since the end of the Cold War.
But Ukraine's military launched air strikes against separatists who had taken over the airport in the eastern capital of Donetsk in what appeared to be the most visible operation of the Ukrainian troops since they started a crackdown on insurgents last month.
In Donetsk, a city of one million, sustained artillery and gun fire was heard from the airport. Fighter jets and military helicopters were seen flying overhead, and dense black smoke rose in the air.
Vladislav Seleznyov, a spokesman for Kiev's anti-terrorist operation, wrote on his Facebook account that the military had given an ultimatum to the armed men who had occupied the airport to lay down their arms. He said the gunmen didn't comply and the military launched an air strike.
Denis Pushilin, a leader of the separatists, said they had sent their men to the airport after some of their supporters were detained.
Many flights to or from Donetsk were delayed or cancelled. Access to the airport was blocked by police.
In Kiev, international observers hailed Ukraine's presidential vote as a "genuine election," saying it was held freely and fairly.
Candy magnate Mr Poroshenko, known for his pragmatism, supports building strong ties with Europe but also has stressed the importance of mending relations with Moscow.
Upon claiming victory in Sunday's vote, he said his first step as president would be to visit the Donbass eastern industrial region, where pro-Russia separatists have seized government buildings, declared independence and battled government troops in weeks of fighting.
"Peace in the country and peace in the east is my main priority," Mr Poroshenko said, signalling that he would bring to an end the Ukrainian army's much-criticised campaign to drive out the armed pro-Russia separatists.