Russia has launched a “massive missile attack” on Ukraine, officials said, knocking out power and forcing people to take cover in shelters across the country.

Authorities on social media reported explosions in the capital Kyiv, southern Kryvyi Rih and northeastern Kharkiv on Friday as air raid sirens were sounded across the country warning of a fresh devastating barrage of Russian strikes on critical energy facilities and infrastructure.

The Black Sea region of Odesa was also targeted, including the central cities of Vinnytsia, Poltava, and the northern Sumy region.

There was no immediate word of casualties, as air defence systems went into operation across Ukraine.

It was also unclear what infrastructure had been hit.

People were thought to be trapped under the rubble of a residential building which was hit in Kryvyi Rih, local officials said.

“The enemy is massively attacking,” Oleksii Kuleba, head of Kyiv’s regional military administration, said in a post on Telegram.

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“Do not ignore air raid alerts, remain in shelters,” Kyrylo Tymoshenko, deputy head of the president’s office, wrote on the messaging app.

Kyiv Mayor Vitali Klitschko reported explosions in the northeastern Desnianskyi and western Holosiivskyi districts, urging residents to go to shelters.

“The attack on the capital continues,” he wrote.

Following several key battlefield losses by Russian forces in recent months, strikes targeting energy infrastructure have been part of Moscow’s new strategy to try to freeze Ukrainians into submission.