(AFP) - A Russian strike battered the regional government building in the southern Ukrainian city of Mykolaiv, a key port under heavy assault for weeks, the regional governor said on Tuesday.

"The regional administration building was hit," governor Vitaly Kim wrote on Facebook. He said that most people inside the building had not been injured but several civilians and soldiers were unaccounted for.

AFP journalists on the scene in the aftermath of the attack said the bodies of two people were pulled from debris.

"We're clearing the rubble. Half the building was destroyed. My office was hit," Kim said in a video statement.

AFP footage showed a tall and grey administrative building, with a large section torn away and debris littering nearby streets.

"Eight civilians are still under the rubble. We hope to be able to get them out," Kim said.

"We are also looking for three soldiers".

Russian attacks on Mykolaiv, which had been under heavy assault for weeks, appeared to be easing recently.

The frontlines seemed to have receded from Mykolaiv, with a Ukrainian counteroffensive being mounted in Kherson, about 80 kilometres (50 miles) to the southeast.

"I was having breakfast in my apartment," Donald, 69, from Canada, told AFP journalists in Mykolaiv.

"I heard a whoosh, then a boom and my windows rattled".

"It's scary. We have been lucky here in Mykolaiv. We haven't had that many explosions in the centre of the city," the retired Canadian postal worker with Ukrainian residency added.

Mykolaiv is a key city on the road to Odessa, Ukraine's biggest port, and its capture would represent a serious gain in Russia's invasion of Ukraine, launched in late February.

© Agence France-Presse