A fierce exchange of attacks between Russia and Ukraine is continuing across the border.

Russia launched a missile strike on the key town of Izium in eastern Ukraine's Kharkiv region on Tuesday. The local governor says five people were killed and 50 others were injured, including three children.

The governor says Russian short-range Iskander ballistic missiles were used in the attack. He says residential apartments and the Izium City Council's administrative building were damaged.

In a social media post, Ukrainian President Volodymyr Zelenskyy said: "This brutality cannot be tolerated. Maximum pressure must be applied to Russia -- through military force, sanctions and diplomacy -- to stop the terror and protect lives."

Meanwhile, the Ukrainian military said on Monday that it had struck an oil refinery in the Volgograd region and a gas processing plant in the Astrakhan region, both in southern Russia.

Local authorities in those regions say fires broke out following the drone attacks. Footage from Astrakhan shows raging flames at the site.

Since last month, Ukraine has carried out a series of attacks on strategic facilities that supply fuel to Russia's military.