On Sunday Russia declared the United States responsible for a Ukrainian missile attack on Russian-annexed Crimea which they report killed four people, including two children, and wounded over 100.

A missile exploded above the city of Sevastopol, releasing shrapnel over people relaxing in a beach area, Russian-appointed officials said.

Russia's defense ministry said Washington and Kyiv bore "responsibility for a deliberate missile strike on peaceful residents," which reportly used U.S.-supplied ATACMS missiles.

Sevastopol governor Mikhail Razvozhayev initially said in a Telegram video the attack had killed three children and two adults and wounded nearly 120 people.

He later revised the death toll to four and numbered 151 people requiring medical care, of whom 82 were hospitalized.

Russian President Vladimir Putin called to "offer his condolences", Razvozhayev added.

The Black Sea port city and naval base on the Crimean peninsula was annexed by Russia in 2014 but is still internationally recognized as part of Ukraine.

Sevastopol regularly comes under fire from Ukraine but Sunday's attack was unusually deadly. Razvozhayev said the attack hit Uchkuyevka, an area with sandy beaches and hotels.

Videos posted on social media showed people running from the beach as explosions went off and people in swimsuits carrying a stretcher. AFP could not verify their authenticity.

A local news channel on Telegram, ChP Sevastopol, cited witnesses as saying that an elderly woman was killed as she swam in the sea.

Washington said in April that it had provided long-range ATACMS missile systems to Kyiv, which had long begged allies for weapons allowing them to strike farther into Russia and beyond the front lines.

Neither the United States nor Ukraine has commented on the Sevastopol strike.

'Terrorist act'

The investigative committee, which probes major crimes, said it was opening an investigation into "a terrorist act."

The governor said Ukraine launched five missiles that Russian air defenses intercepted over the sea but fragments fell onto the shore, wounding people.

Razvozhayev said shrapnel hit beach areas in the north of the city and set fire to a house and a woodlot.

A Russian defense ministry statement said Ukraine had committed a "terrorist attack on the civilian infrastructure of Sevastopol with U.S.-supplied ATACMS tactical missiles loaded with cluster warheads."

The ministry said four missiles were downed but a fifth changed trajectory after being intercepted "with its warhead exploding in the air over the city."

It added that "all flight missions for U.S. ATACMS are launched by U.S. specialists based on the U.S.'s own satellite reconnaissance data.

"Such actions will not be left without a response," the ministry said.

Ukraine's military has not commented on the attack, which came a day after a Russian-guided bomb strike on the city of Kharkiv hit an apartment building, killing two people and wounding more than 50.

Russia's complaints come just a day after it attacked an entire Ukrainian energy grid destroying key infrastructure and injuring two power plant workers.

Deaths in Belgorod, Russia

On Sunday, Russian strikes hit a house and a children's educational center in Kharkiv, killing one person and injuring 10, including two teenagers, regional governor Oleg Synegubov said.

In the Belgorod region on Sunday, three Ukrainian attack drones struck Graivoron, near the border with Ukraine, said governor Vyacheslav Gladkov.

"A peaceful civilian was killed. The man died from his wounds at the spot," and three people were wounded, Gladkov wrote on Telegram.

In a social media post, Ukrainian President Volodymyr Zelensky urged allied countries to help Ukraine step up attacks on Russian soil.

"We have enough determination to destroy terrorists on their territory -– it is only fair -- and we need the same determination from our partners. We can stop Russia," Zelensky wrote.

In his evening address, he added: "The recent approval of strikes on Russian territory -- near the border -- made it possible to destroy part of Russia's terrorist potential."

But, he said, "We need more long-range weapons, we need appropriate weapons for Ukrainians."

Ukraine's energy operator Ukrenergo announced that rolling electrical blackouts would be imposed nationwide all of Monday because of increased Russian attacks on power stations.