KIEV, May 26 - Ukraine launched air strikes and a paratrooper assault against pro-Russian rebels who seized an airport on Monday, as its newly elected leader rejected any talks with "terrorists" and said a robust military campaign in the east should be able to put down a separatist revolt in "a matter of hours,” Reuters reported.

Ukrainians rallied overwhelmingly in Sunday's election behind Petro Poroshenko, a political veteran and billionaire owner of chocolate factories, hoping the burly 48-year-old can rescue the nation from the brink of bankruptcy, civil war and dismemberment by its former Soviet masters in the Kremlin.

Monday's rapid military response to separatists who seized the airport in Donetsk was a defiant answer to Moscow, which said it was ready for dialogue with Poroshenko but demanded he first scale back the armed forces' campaign in the east.

Even as the fighting was getting under way, Poroshenko held a news conference in Kiev where he said the government's military offensive needed to be "quicker and more effective.”

"The anti-terrorist operation should not last two or three months. It should last for a matter of hours," he said.

As for the rebel fighters: "They want to preserve a bandit state which is held in place by force of arms," he said. "These are simply bandits. Nobody in any civilized state will hold negotiations with terrorists."

Gunfire and explosions could be heard as a warplane flew over Donetsk's Sergei Prokofiev International Airport, hours after truckloads of armed rebel fighters arrived and seized a terminal. Thick black smoke rose from within the perimeter.

The government said its jets had strafed the area with warning shots and then struck a location where rebels were concentrated, scattering the fighters before paratroops were flown in to face them.

Eight hours after it began, fighting was continuing after nightfall and had spread to residential neighborhoods nearby.

"Fighting continues in the airport, with the use of planes and helicopters," said separatist leader Denis Pushilin. "It's a full-blown military standoff. I have no information on casualties. Our groups have destroyed one helicopter of the enemy."

At one point, three Ukrainian Mi-24 helicopter gunships fired rockets and cannon at the concrete and glass terminal. More plumes of black smoke shot up into the air as the helicopters fired at targets on the runway. The gunships threw out decoy flares as fighters shot at them from the ground.

Russia's foreign ministry urged Kiev to halt what it called "military operations against its own people" and said it wanted the Organization for Security and Cooperation in Europe to investigate clashes with pro-Russian separatists in Donetsk.

Pushilin called for "any available help from the Russian people.”

Preliminary results, with 80 percent of the vote counted, gave Poroshenko 54.1 percent of the vote - towering over a field of 21 candidates with enough support to avert a run-off. His closest challenger, former premier Yulia Tymoshenko, had just 13.1 percent and made clear she would concede.

Poroshenko's most urgent task is finding a modus vivendi with the giant neighbor that has seemed poised to carve Ukraine up since mass protests in Kiev toppled a pro-Russian president in February.

Poroshenko said Moscow's "argument about legitimacy has disappeared" as he had also topped the polls among those who were able to cast ballots in the eastern regions of Donetsk and Luhansk.

"I hope Russia will support efforts to tackle the situation in the east," Poroshenko said. He said he planned to meet Russian officials in the first half of June.

But he showed no sign of heeding Moscow's demand that he call off the operation against rebels in the east.

"Protecting people is one of the functions of the state," he said, promising to invest more in the army. "The Ukrainian soldier should no longer be naked, barefoot and hungry."

So far, Ukraine's military forces have had little success against rebels who have declared independent "people's republics" in two provinces of the eastern industrial heartland where about 20 people have been killed in recent days.

Ukrainian officials say they have held back from using full force in part to avoid provoking an invasion from tens of thousands of Russian troops massed on the frontier.

Questions have also been raised about Ukrainian forces' training, equipment and loyalties. (rt/ez)