By Gabriela and Baczynska
DONETSK Ukraine (Reuters) - Armed pro-Russian separatists took over Donetsk's international airport terminal in eastern Ukraine on Monday after forcing its closure to flights and Reuters journalists later heard gunfire and explosions in the vicinity.
The journalists also saw smoke billowing from somewhere inside the airport perimeter as a warplane flew high overhead. A Reuters photographer earlier saw three trucks carrying dozens of armed men towards Sergei Prokofiev International Airport.
Donetsk, a city of a million that is effectively the capital of the industrial Donbass region, is largely in the hands of pro-Russian separatists who prevented local people taking part in Ukraine's presidential election on Sunday.
The gunfire erupted at the airport shortly after the election victor, Petro Poroshenko, said during a news conference in the Ukrainian capital Kiev that he would not negotiate with "terrorists" in eastern Ukraine.
Donetsk airport authorities announced its closure to flights earlier on Monday after the separatists came to the facility to demand the withdrawal from the area of Ukrainian forces, who have been policing the perimeter.
"The rebels are in the terminal. The rest of the airport area is controlled by the (Ukrainian) National Guard. The two sides are in talks now," airport spokesman Dmitry Kosinov told Reuters before the gunfire broke out.
The pro-Moscow rebels have declared autonomous "people's republics" in the regions of Donetsk and Luhansk following makeshift referendums on May 11. They say the two regions are no longer part of Ukraine.
Only about 20 percent of the two regions' polling stations functioned in Sunday's presidential election and many voters stayed at home, fearful for their safety. No polling stations were open in the city of Donetsk.
A spokeswoman for the separatists said the group now at the airport was the "East" battalion which took part in clashes last Friday with a Ukrainian militia just west of Donetsk in which at least two people were killed.
(Additonal reporting by Yannis Behrakis; Writing by Gareth Jones; Editing by Alastair Macdonald)