Pro-Russian rebels in eastern Ukraine are claiming that they have seized control of the Donetsk airport after days of intense fighting. Ukrainian officials have not confirmed a retreat.

Rebel leader Alexander Zakharchenko said at a press conference early Monday in Donetsk that the rebels had taken control of the airport.

The separatist stronghold was shaken by intense outgoing and incoming artillery fire over the weekend as a bitter battle raged for the air terminal and surrounding areas. Sporadic explosions could still be heard from the direction of the airport early Monday.

The U.N. estimates that more than 4,700 people have been killed in eastern Ukraine since April.