(Adds separatists returning to airport, other details)
DONESTSK, Ukraine, May 26 (Reuters) - Armed pro-Russian separatists forced a shutdown on Monday of Donetsk airport in eastern Ukraine, an airport representative said, a day after they prevented a majority of the region's voters from taking part in presidential elections.
Earlier this month, the pro-Moscow rebels declared autonomous "people's republics" in the regions of Donetsk and Luhansk after holding makeshift referendums. They say the two regions, which include the Donbass coalfield, 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, home to one million people.
The head of Donetsk airport's press service, Dmitry Kosinov, said dozens of armed representatives of the self-styled "Donetsk People's Republic" had come to the airport in the early hours of Monday morning to demand the withdrawal of Ukrainian troops.
The troops have been policing the perimeter of the Sergei Prokofiev airport. "On the territory of the airport there are armed people. This is ample reason to halt our work on security grounds," Kosinov said in a statement, adding there had been no violence. It was not clear when the airport would reopen.
Reuters journalists at the scene said they saw three open military trucks carrying dozens of separatists with assault rifles heading towards the airport later on Monday morning after being allowed through by a police roadblock.
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.
Confectionary magnate Petro Poroshenko, who claimed victory in Sunday's presidential election after exit polls gave him an absolute majority in a first round of voting, has said that tackling the separatist conflict in eastern Ukraine will be his top priority. (Reporting by Gabriela Baczynska; Writing by Gareth Jones; Editing by Mark Heinrich)