Moscow: Russian President Vladimir Putin on Monday warned of "harsh" reprisals after the Crimea bridge attack on Saturday.

In a television appearance Monday, Putin said Russia had struck military and infrastructure targets across Ukraine following the Crimea bridge blast.

Putin threatened further "harsh" responses that correspond "to the level of threat to the Russian Federation, have no doubt about it," while accusing Kyiv of "terrorism."

In what appears to be the heaviest wave of missile and rocket attacks since the opening week of the war, Kyiv and other Ukrainian cities were rocked by deadly Russian strikes on Monday.

Officials said they targeted critical energy infrastructure and several regions of Ukraine are now suffering power outages.

The Kremlin said today that a huge missile salvo across Ukraine launched by its forces was within the framework of what Russia calls its "special military operation" in Ukraine.

Meanwhile, Ukraine has not claimed responsibility for the attack on the Kerch bridge, a key link between the Russian mainland and Crimea.

Eleven sites of critical infrastructure have been struck in Kyiv and eight other regions of Ukraine, according to Prime Minister Denys Shmyhal.

Some of the regions are experiencing blackouts," Shmyhal said. "We must be ready for temporary disruptions with power connections and water supply."

A senior Ukrainian military official has said "generations of Russians will answer" for a wave of explosions that struck multiple Ukrainian cities on Monday.

"The Russians are shameful losers. Did you intend to scare us?" Andrii Yermak, head of President Zelenskyy's office, said of the attacks.

"There will be a harsh response to every hit. You will be held responsible for every death and suffering. And not only you. Entire generations of Russians will answer," Yermak said on Telegram.

"We will continue to destroy every one who comes to Ukraine with weapons. These hits make us even angrier. These hits will only speed up our progress.

"We are not afraid. We are only getting angrier and more accurate," Yermak added.

Powerful explosions rang across Kyiv on Monday morning, leaving multiple people dead. At the same time, regional authorities also reported missile and rocket attacks in Kharkiv, Lviv, Mykolaiv and Dnipropetrovsk, partly aimed at critical civilian infrastructure.

Ukrainian President Volodymyr Zelenskyy said the missile strikes targeted Ukraine's energy facilities and its people.

"They have especially chosen the time and the targets to create the most damage," he said while standing outside his office in the center of Kyiv.

Moscow wanted to destroy Ukraine's "energy system," Zelenskyy said, adding that the Ukrainians shot down 38 incoming projectiles. He urged people to stay in shelters on Monday.

Further south, a Ukrainian official also confirmed that Russian missiles are targeting power infrastructure in the Mykolaiv region.

"They are hitting the infrastructure, trying to leave us without electricity," Vitalii Kim, head of Mykolaiv regional military administration, said on Telegram.

After reports of Russian missile attacks across Ukraine on Monday morning, Kyiv's Foreign Minister Dmytro Kuleba said on Twitter that Russian President Vladimir Putin "will not break Ukraine down."

"Putin's only tactic is terror on peaceful Ukrainian cities, but he will not break Ukraine down. This is also his response to all appeasers who want to talk with him about peace: Putin is a terrorist who talks with missiles," Kuleba tweeted.

Amid multiple explosions in Kyiv and other Ukrainian cities early Monday, Zelenskyy said Russia was trying to annihilate Ukraine.

The series of Russian missiles launched at Ukraine on Monday morning was aimed at "critical infrastructure to destroy the country's energy supply," according to a Ukrainian government official.

Kyrylo Tymoshenko, deputy head of the Office of the President of Ukraine, also warned Ukrainians to be prepared for blackouts.

"Power facilities from Lviv to Zaporizhzhia, Kyiv to Khmelnytskyi region, Dnipro and Vinnytsia, Ivano-Frankivsk region, Sumy region, Kharkiv region, Zhytomyr region, Kirovohrad, and the entire south are targeted," Tymoshenko said on Telegram.

"This may affect the stability of energy supply, so we need to be prepared for the consequences of such shelling, up to rolling blackouts," he added.

The Ukrainian State Emergency Service said there is no electricity supply in five regions -- Lviv, Poltava, Sumy, Kharkiv and Ternopil -- and power supply has been partially disrupted in the rest of the country.

Meanwhile, the G7 group of nations will hold an emergency meeting via video conference on Tuesday, the office of German Chancellor Olaf Scholz confirmed to CNN. Scholz is the current G7 president under its rotating leadership.

Ukrainian President Volodymyr Zelenskyy said that he would address the meeting. "My speech is scheduled, in which I'll tell about the terrorist attacks by [the Russian Federation], he said on Twitter.

The G7 consists of the seven leaders from some of the world's largest economies: Canada, France, Germany, Italy, Japan, the United Kingdom and the United States. Russia was indefinitely suspended from the group -- then the G8 -- in 2014 after its illegal annexation of Crimea.

At least 10 people have died and 60 are injured in Ukraine after a wave of Russian attacks across the country on Monday morning, police spokesperson Maryana Reva said in an interview on Ukrainian TV. Multiple European political figures roundly condemned Russia's spate of attacks on Ukrainian cities on Monday.

"Deeply shocked by Russia's attacks on civilians in #Kyiv and other cities in Ukraine. Such acts have no place in (the) 21st century. I condemn them in the strongest possible terms," the European Union's foreign policy chief, Josep Borrell said. "We stand with Ukraine. Additional military support from the EU is on its way," Borrell tweeted Monday.

"Again, Putin is massively terrorizing innocent civilians in Kyiv and other cities in [Ukraine]. (The Netherlands) condemns these heinous acts. Putin does not seem to understand that the will of the Ukrainian people is unbreakable. Ukraine remains determined, and we continue to support Ukraine," Dutch Prime Minister Mark Rutte tweeted.

Belgium's Prime Minister Alexander De Croo tweeted that the "bombardment of Kyiv and of civilian targets in many other cities is a reprehensible act by Russia. It is an unacceptable escalation of violence that strengthens Belgium's resolve in supporting the people of Ukraine and their brave fight for a free and sovereign nation."

"Shocking images are coming once again from Ukraine this morning! I strongly condemn Russian missile attacks against civilian targets and critical infrastructure in Ukraine. The only intention behind these attacks is to terrorize the civilian population. Stay strong Ukrainians!" tweeted Luxembourg's Prime Minister Xavier Bettel.

Slovakian Prime Minister Eduard Heger tweeted that he condemns "today's cowardly attacks of Russian forces on #civilians and civilian infrastructure in #Ukraine.

French Foreign Minister Catherine Colonna also tweeted to condemn the attacks. "I condemn in the strongest terms today's indiscriminate Russian strikes against Ukrainian cities. Intentionally targeting civilian populations is a war crime," she said.

And Italy also reiterated its "unwavering and steadfast support for Ukraine, its people and its resilience."

The Italian foreign ministry said it was "horrified by the cowardly missile attacks which hit the centre of Kyiv and other Ukrainian cities."