KIEV, Ukraine -- Scores of pro-Russia gunmen have been killed in two days of fighting at the international airport in the Ukrainian city of Donetsk after ignoring a government ultimatum to lay down their weapons or face a military operation that won't cease until there isn't a separatist fighter left, Ukrainian officials and Russian media reported Tuesday.

Moscow's state-controlled television and news agencies quoted leaders of the breakaway "People's Republic of Donetsk" as saying more than 50 fighters died in an attempt to take control of the modern Sergei Prokofiev International Airport, Ukraine's second-largest and a vital transport hub for the eastern city of 1 million.

Militants last week succeeded in taking over the train station in Donetsk and have been thwarting passenger transportation and shipment of goods in and out of the main city in eastern Ukraine's Donbass industrial belt.

The stepped-up government offensive against the pro-Russia rebels has coincided with Ukraine's Sunday election of billionaire candy maker Petro Poroshenko to serve as president after a June 15 inauguration. Poroshenko will replace Viktor Yanukovich, the Kremlin-allied head of state forced from power in February by a fierce rebellion sparked by his decision to scrap closer ties with the European Union in favor of the country's traditional alliance with -- and domination by -- Moscow.

Poroshenko vowed Monday to drive out the "terrorists" occupying a dozen towns and cities in eastern Ukraine, just as truckloads of the militants toted rocket launchers to the Donetsk airport and for a time occupied the sleek new terminal built for the city's hosting of a 2012 European soccer championship game.

Poroshenko said at a news conference Monday that he wouldn't negotiate with anyone using force and likened the gunmen claiming power in Donetsk and Luhansk to Somali pirates spreading violence and lawlessness.

But the president-elect, declared the winner Tuesday after a tally of more than 90% of the ballots gave him a decisive 55% in a field of 21 contenders, said he hoped to engage the Kremlin in talks to resolve the crisis that many here believe was instigated by Russian President Vladimir Putin.

In a conversation with Italy's new prime minister Tuesday, Putin issued a veiled threat to the incoming Ukrainian leader, calling for an immediate end to what he called "the punitive operation conducted by the army in the southeast region."

Russian officials have cast the Ukrainian government's counteroffensive to retake territory and buildings seized by the militants over the past two months as a campaign to wipe out the Russian-speaking minority in the east. Putin has also referred to the separatist-occupied areas in the Donetsk and Luhansk regions as "Novorossiya," a name applied to the area when it was conquered and annexed by Russia in czarist times.

Oleksandr Boroday, the self-styled prime minister of the breakaway Donetsk region, which was proclaimed an independent country by the militants May 12, said the death toll from the fighting could surpass 100. He claimed half of the victims were civilians and accused Ukrainian troops of firing on wounded fighters.

Vladyslav Selezniov, a military spokesman for the Kiev government, said that the militants' reports of civilian casualties were grossly distorted.