DONETSK, Ukraine — The eastern city of Donetsk was in turmoil Tuesday a day after government forces used fighter jets to stop pro-Russia separatists from taking over the airport. Dozens were reported killed and the mayor went on television to urge residents to stay indoors.

The city of 1 million was engulfed by fighting Monday when rebels moved to seize the airport, Ukraine’s second largest. They were repelled by government forces using combat jets and helicopter gunships. Associated Press journalists witnessed intensive gun fire throughout the day and into the night. Plumes of black smoke rose into the air and officials shut down Donetsk airport and nearby streets to traffic amid the fighting.

Donetsk mayor Oleksandr Lukyanchenko said 40 people, including two civilians, were killed in Monday’s fighting. Rebel leaders, meanwhile, said the deaths could reach up to 100.