Ukraine's energy minister has accused Russia of mounting the largest wave of attacks on his country's energy sector since Moscow launched its invasion in 2022.

German Galushchenko told a news conference on Monday that up to 80 percent of thermal power stations was attacked in recent weeks. He said more than half of Ukraine's hydroelectric plants were also hit.

Russian forces have unleashed rounds of attacks on infrastructure targets in Ukraine since late last month, causing large-scale power outages in the eastern region of Kharkiv and the southern region of Odesa.

In other parts of Ukraine, the governor of the southern region of Zaporizhzhia says a Russian missile strike killed four people.

Two other people were killed in Russian attacks in the northeastern region of Sumy and Poltava region in the central Ukraine.

Ukraine's defense intelligence service said in a social media post that a fire disabled the Russian missile ship Serpukhov on Sunday. The ship was anchored at a naval base in the Russian exclave of Kaliningrad on the Baltic Sea coast.

A Ukrainian media outlet says a source from Ukraine's military intelligence confirmed that its operatives were behind the fire. The outlet says it was the first attack on Russian naval assets in the Baltic Sea.

The fire is believed to be part of Ukraine's continued military campaigns in Russia.