KYIV, Sep 25 (AFP) - Ukraine has received US Abrams battle tanks, President Volodymyr Zelensky announced Monday, boosting Kyiv's forces as they seek to break through heavily-fortified Russian defensive lines.

The announcement came just after Ukraine claimed it had killed the commander of Russia's Black Sea fleet in a missile strike on Moscow's naval headquarters in Crimea last week in what would be a major embarrassment for Russia.

"Abrams are already in Ukraine and are preparing to reinforce our brigades," Zelensky said on social media.

Ukraine has repeatedly asked for more Western weapons, including longer-range missiles, to help break through Russian positions and launch strikes deep within Russian-controlled territory.

Zelensky did not elaborate on how many tanks had arrived, nor on how long it would take for them to be deployed to the front line.

"I am grateful to our allies for fulfilling the agreements. We are looking for new contracts and expanding the geography of supply," he said.

Washington had promised to provide 31 Abrams tanks to Kyiv at the start of the year, part of more than $43 billion in security assistance pledged by the United States since Moscow invaded in February last year.

Russia has repeatedly denounced the arms shipments to Ukraine, arguing they "prolong" the conflict and risk causing it to spiral out of control.

Moments before Zelensky's announcement, Ukraine claimed it killed the commander of Russia's Black Sea fleet in a missile strike on Moscow's naval headquarters in annexed Crimea on Friday.

The strike dealt a serious blow to Moscow, which has suffered a string of attacks on the strategically important port of Sevastopol over the past months.

"Thirty-four officers were killed, including the commander of the Black Sea fleet. Another 105 occupiers were wounded," Ukraine's special forces said in a statement.

The attack sent plumes of black smoke spiralling over the building in central Sevastopol, the largest city in the Crimean peninsula which was annexed by Russia in 2014.

"The headquarters are beyond repair," the special forces added in the statement.

Russia's defence ministry said on the day of the attack that one serviceman was missing, without providing any further detail.

Ukrainian and Russian attacks in and around the Black Sea have increased since Moscow withdrew from an accord that allowed safe passage to civilian cargo ships from three Ukrainian ports.

Photo from AP