Ukraine President Volodymyr Zelenskyy has visited frontline soldiers in the southern Ukrainian region of Mykolaiv.

Ukraine's presidential office posted a video of his visit on Saturday.

Zelenskyy inspected a regional administration building that had been destroyed by Russian forces. He was briefed on the fighting in southern Ukraine on the Black Sea.

He also visited a hospital and handed out medals to people there.

In Ukraine, Russian forces are intensifying the offensive in a bid to take full control of the eastern region of Luhansk.

They have been striving to besiege the key city of Severodonetsk in eastern Ukraine.

Ukrainian civilians and soldiers remain stranded in the Azot chemical plant in the city. Russian officials have been urging them to surrender while they call for humanitarian corridors to help the civilians evacuate. They say some Russian troops have already entered the plant and are fighting against Ukrainians.

The Russian Defence Ministry announced on Saturday that its forces destroyed oil refining and fuel facilities as they bombarded Lysychansk, a city neighboring Severodonetsk.

The Institute for the Study of War, a US think tank, reported on Friday that Russia continues to deploy additional troops in the Severodonetsk and Lysychansk area while "Ukrainian defenses remain strong."

Russian President Vladimir Putin addressed medical professionals during an online meeting on Saturday. He thanked them for saving lives of "comrades-in-arms who are participating in the special military operation."