An overnight blast hit the premises of the US embassy in Kiev but there were no casualties, Ukrainian police said on Thursday.

The explosion hit the mission located in central Kiev shortly after midnight, a statement said.

"Investigators found that an unknown person threw an explosive device on the territory of the diplomatic mission," it said.

The US embassy was not immediately contactable for comment but a diplomat, speaking on condition of anonymity, told AFP: "The embassy will continue to function normally."