Ukraine said Russia had destroyed homes in the south and knocked out power in the north in a new round of missile attacks on Monday as the West tried to limit Moscow's ability to finance its invasion by imposing a price cap on Russian seaborne oil.

Air alerts sounded across Ukraine and officials urged civilians to take shelter from what they said was the latest in waves of Russian missile strikes since its Feb. 24 invasion.

Two people were killed in the Zaporizhzhia region where several houses were destroyed, the deputy head of the presidential office, Kyrylo Tymoshenko, said in one of the first reports of the damage. Buildings had been hit in the suburbs of the city of Zaporizhzhia and some Russian missiles had been shot down, a city official said.

The governor of the Kyiv region said its air defenses were working there, and told residents to remain in shelters. An energy provider said power had been knocked out on the northern region of Sumy in the latest missile strikes.

Russian forces have increasingly targeted Ukrainian energy facilities in recent weeks as they faced setbacks on the battlefield, causing major power outages as winter sets in.

"Don't ignore the alarm," said Andriy Yermak, head of the Ukrainian presidential staff.

Ukraine had only just returned to scheduled power outages from Monday rather than the emergency blackouts it has suffered since widespread Russian strikes on Nov. 23, the worst of the attacks on energy infrastructure that began in early October.

Russia has said the attacks are designed to degrade Ukraine's military. Ukraine says they are clearly aimed at civilians and thus constitute a war crime.

A $60 per barrel price cap on Russian seaborne crude oil came into force on Monday, the latest Western measure to punish Moscow over its invasion. Russia is the world's second-largest oil exporter.

The agreement allows Russian oil to be shipped to third-party countries using G7 and EU tankers, insurance companies and credit institutions, only if the cargo is bought at or below the $60 per barrel cap.

Moscow has said it will not abide by the measure even if it has to cut production. Ukrainian President Volodymyr Zelenskiy said $60 was too high to stop Russia's assault.

A Russian oil blend was selling for around $79 a barrel in Asian markets on Monday - almost a third higher than the price cap, according to Refinitiv data and estimates from industry sources.

On the ground in Ukraine, both sides reported casualties from attacks overnight, on an industrial enterprise and another location in southern Ukraine and on state-run accommodation in Russian-held territory in the east. Reuters was not immediately able to verify those reports.