Russian forces launched a drone attack overnight that targeted a Ukrainian town on the border with NATO member Romania, Ukrainian officials said on Friday.

The attack hit the town of Izmail, Ukraine's biggest port on the Danube river, which is important for critical imports and which lies across the river from Romania.

A post office branch was destroyed in the drone attack, regional Governor Oleh Kiper said.

He reported no casualties.

Reuters could not independently verify the report. There was no immediate comment from Russia.

Both sides deny targeting civilians in the war that Russia started with its full-scale invasion of Ukraine more than three years ago.