KYIV, March 9 - Russia fired a huge wave of missiles across Ukraine on Thursday as people slept, killing at least nine civilians and knocking out power in an attack Kyiv said included six Kinzhal hypersonic cruise missiles, one of Moscow's most valuable weapons, Reuters reported.

The mass strikes on targets far from the front were the first such wave since mid-February and shattered the longest calm since Moscow began an air campaign against Ukraine's civil infrastructure five months ago.

"The occupiers can only terrorize civilians. That's all they can do. But it won't help them. They won't avoid responsibility for everything they have done," said President Volodymyr Zelensky, describing strikes that hit infrastructure and residential buildings in ten regions.

Russia's defense ministry said it had carried out a "massive retaliatory strike" as payback for a cross-border raid last week. It claimed to have hit all its intended targets, destroying drone bases, disrupting railways and damaging facilities that make and repair arms.

Moscow says such hits are intended to reduce Ukraine's ability to fight. Kyiv says the air strikes have no military purpose and aim to harm and intimidate civilians, a war crime.

In the capital Kyiv, a seven-hour alert through the night was the longest of Russia's five-month air campaign.

Moscow confirmed it had used hypersonic Kinzhal - Russian for dagger - missiles in Thursday's attack. Ukrainian officials said it was the first time they had faced so many of the weapons, which Ukraine has no way to shoot down.

The White House said that the barrage was "devastating" to see and Washington would continue to provide Ukraine with air defense capabilities.

Russia is believed to have just a few dozen Kinzhals, which fly many times faster than the speed of sound and are built to carry nuclear warheads with a range of more than 2,000 km (1,200 miles). In his speeches, President Vladimir Putin regularly touts the Kinzhal as a weapon for which the transatlantic NATO alliance backing Kyiv has no answer.

Ukraine said the attacks had knocked out power in various places including to the Zaporizhzhia nuclear power plant, Europe's largest, severing it from the grid and forcing it onto emergency diesel power to prevent a meltdown. It was later reconnected to Ukraine's energy grid, operator Ukrenergo said.

The plant, which Russia has held since capturing it early in the war, is near the front line and both sides have warned in the past of a potential for disaster. Moscow said it was safe.

U.N. nuclear watchdog chief Rafael Grossi appealed for a protection zone around the plant.

"Each time we are rolling a dice. And if we allow this to continue time after time then one day our luck will run out," Grossi told the IAEA's 35-nation Board of Governors. (rt/ez)