Ukraine says it has recaptured the airport in the eastern city of Donetsk after a day of air strikes and fierce gun battles with pro-Moscow separatists that left at least 48 people, including two civilians, dead.

"The airport is under our full control. The enemy suffered heavy losses. We have none," Interior Minister Arsen Avakov said in a statement on Tuesday.

He said, however, that the military was continuing its operation at the airport and AFP journalists reported hearing sporadic gunfire and explosions during the day.

According to Interfax-Ukraine, the Ukrainian State Aviation Service has said the airport will stay closed until the evening of May 28.

The Organization for Security and Cooperation in Europe (OSCE) also reported that it had lost contact with a four-member observer team based in the restive city since Monday evening.

The battle for the main transport hub in Ukraine's industrial heartland erupted on Monday just hours after president-elect Petro Poroshenko vowed to take a tough stand against the "terrorists".

Russian President Vladimir Putin immediately called on Ukraine to end its "punitive" operation in the rebel-held east and for talks between Kiev and the pro-Russian separatists.

The bodies of 30 pro-Russian rebels have been brought to a hospital, according to separatist sources.

A rebel fighter told the Associated Press that a lorry carrying the bodies was still parked outside the hospital, waiting for explosives experts to check it for any unexploded ordnance.

Al Jazeera's Jacky Rowland, reporting from Kiev, said the fighting had been the most intense since the victory of Poroshenko.

"Now we are seeing a concerted and focused operation," Rowland said, adding that Poroshenko's "very convincing victory" has given the "mandate to take decisive action".

Poroshenko is set to meet US President Barack Obama when the American leader visits Europe from June 3 to 6.

'Disbelief and shock'

Al Jazeera's John Wendle, reporting from Donetsk, said: "After last night's fight, a feeling of disbelief and shock seems to be building as an expectant atmosphere takes hold with people waiting for the next move by the armed sides."

On Monday the armed separatists seized the international airport in Donetsk, prompting a closure. Later in the day they came under attack from Ukrainian security forces.

Plumes of black smoke rose in the air. The city mayor went on television advising residents to stay at home.

President-elect Poroshenko has pledged to negotiate a peaceful end to the pro-Russian uprising in the east, where rebels have seized government offices and fought Ukrainian troops for more than a month.

Yet Poroshenko described the separatists as "Somali pirates", saying that arms should be used against "killers and terrorists", but he also indicated that he wanted a quick end to the military operation in the east.

"The anti-terrorist operation cannot and should not last two or three months," he said. "It should and will last hours."

The latest developments imperils an initiative by Poroshenko and Sergey Lavrov, the Russian foreign minister, to hold a dialogue and resolve the Ukrainian crisis diplomatically.

Lavrov said on Monday that a dialogue was only possible if Ukraine refrained from cracking down on pro-Russian separatists.

PHOTO CAPTION

Intense fighting broke out in eastern Ukraine on Monday when government air and ground forces attacked pro-Russian separatist gunmen who had seized an airport terminal.

Aljazeera