DONETSK, Ukraine - The airport of a restive eastern Ukrainian city has been closed, one day after troops mounted an offensive against pro-Russian forces that killed at least a dozen people.

A statement published on the Donetsk airport website Tuesday said that the facility was closed for departing and arriving flights because of a government order.

Ukraine's government gave no information about the closure, and the airport spokeswoman said she hadn't received any information about how long the closure would last.

On Monday, pitched gunbattles killed at least four Ukrainian officers as well as at least eight other people, both civilians and pro-Russian militants.

The Ukrainian army has struggled to regain control over the restive east, where pro-Russian forces have seized government buildings and police stations across at least a dozen towns.