A firefighter walks outside a destroyed apartment building after a bombing in Kyiv, Ukraine. AP

Russian bombers have likely been launching heavy 1960s-era anti-ship missiles in Ukraine, the UK Defence Ministry said. The Kh-22 missiles were primarily designed to destroy aircraft carriers using a nuclear warhead. When used in ground attacks with conventional warheads, they "are highly inaccurate and therefore can cause severe collateral damage and casualties,” the ministry said.

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Fierce fighting in east Ukraine as Zelensky says world must not look away

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Both sides have expended large amounts of weaponry in what has become a grinding war of attrition for the eastern region of coal mines and factories known as the Donbas, placing huge strains on their resources and stockpiles.

Russia is likely using the 5.5-tonne (6.1-ton) anti-ship missiles because it is running short of more precise modern missiles, the British ministry said. It gave no details of where exactly such missiles are thought to have been deployed.

Ukrainian soldiers carry a body of a civilian killed by the Russian forces in Irpin close to Kyiv, Ukraine. AP

As Russia also sought to consolidate its hold over territory seized so far in the 108-day war, the US defence secretary said Moscow's invasion of Ukraine "is what happens when oppressors trample the rules that protect us all.”

"It’s what happens when big powers decide that their imperial appetites matter more than the rights of their peaceful neighbors,” Lloyd Austin said during a visit to Asia. "And it’s a preview of a possible world of chaos and turmoil that none of us would want to live in.”

A Ukrainian governor accused Russia of using incendiary weapons in a village in the eastern province of Luhansk, southwest of the fiercely contested cities of Sievierodonetsk and Lysychansk.

While the use of flamethrowers on the battlefield is legal, Luhansk Gov. Serhii Haidai alleged the overnight attacks in Vrubivka caused widespread damage to civilian facilities and an unknown number of victims.

A destroyed house is pictured in the village of Yatskivka, eastern Ukraine. AFP

"At night, the enemy used a flamethrower rocket system - many houses burnt down,” Haidai wrote on Telegram on Saturday. His claim could not be immediately verified.

Sievierodonetsk and neighbouring Lysychansk are the last major areas of Luhansk remaining under Ukrainian control. Haidai said Russian forces destroyed railway depots, a brick factory and a glass factory.

The Ukrainian army said Saturday that Russian forces also were to launch an offensive on the city of Sloviansk in Donetsk province, which together with Luhansk makes up the Donbas,

Moscow-backed rebels have controlled self-proclaimed republics in both provinces since 2014.

Associated Press