A Ukrainian helicopter Mi-24 gunship fires its cannons against?armed activists?at the main terminal building of Donetsk international airport May 26, 2014.[Photo/Agencies]

KIEV - At least 40 people, including two civilians were killed in fierce fighting between armed activists and government troops in Ukraine's eastern city of Donetsk, authorities said Tuesday.

Ukraine Crisis

According to Donetsk mayor Alexander Lukyanchenko, dozens of others were injured in the government's operation to retake the international airport of the city.

The battle began on Monday when Ukrainian troops launched airstrikes against armed activists, who took control of the airport earlier in the day and responded with automatic weapon and grenades.

By early Tuesday, government troops had forced the militants to withdraw from the airport and put it under control.

The clashes happened just one day after a presidential election was held in the eastern European country.

Preliminary results showed independent politician Petro Poroshenko was a likely winner, taking a comfortable lead with 54.45 percent of over 95percent of the ballots accounted. Former Prime Minister Yulia Tymoshenko conceded defeat with only 12.8 percent of the vote.

On Monday, Poroshenko said he wanted to negotiate with protesters to end the crisis, but emphasized he would not talk with terrorists.