Russia launched missile strikes on cities across Ukraine on Monday in response to what the Russian president called “a terrorist act”.
Speaking at the opening of a meeting of Russia's Security Council, Mr Putin said “a massive strike was carried out with long-range, high-precision air, sea and land-based weapons on Ukraine's energy, military command and communications facilities”.
Any further attacks would be met with a response that would “correspond to the level of threats posed”, he said.
Explosions rocked several cities across Ukraine on Monday.
The head of the Ukrainian military said Russian forces launched at least 75 missiles at Ukraine, with fatal strikes targeting the capital Kyiv, as well as cities in the south and west.
About 40 rockets were shot down by Ukraine's air defences, officials said.
President Volodymyr Zelenskyy said there were some dead and wounded, as he accused Russia of trying to wipe his country “off the face of the Earth”.
“The air raid sirens do not subside throughout Ukraine,” Mr Zelenskyy said on the Telegram messaging app. “There are missiles hitting. Unfortunately, there are dead and wounded.”
The strikes, some of which featured Iran-made drones, were timed to inflict the greatest possible losses, the Ukrainian president said.
“They want panic and chaos, they want to destroy our energy system,” Mr Zelenskyy said in a video post that showed him outside his presidential office.
“The second target is people. Such a time and such targets were specially chosen to cause as much damage as possible.”
Moscow's Defence Ministry said it had hit “all designated targets” in the missile attack, which represented one of the largest co-ordinated Russian strikes on Ukraine since the first weeks of the war.
Leaders of the Group of Seven — an informal bloc of industrialised democracies, made up of the US, Canada, France, Germany, Italy, Japan and the UK — will discuss the attacks on Tuesday.
They will take part in an emergency video conference that will also be joined by Mr Zelenskyy, sources said.
Mr Zelenskyy said he had spoken to German Chancellor Olaf Scholz, whose country holds the current G7 presidency.
The Ukrainian leader also spoke to his French counterpart, Emmanuel Macron, to discuss air defence for Ukraine, with “the need for a tough” international response to the missile attacks.
Mr Putin, meanwhile, said forensic and other data, as well as operational information, indicated Saturday's explosion on the bridge linking Crimea was “a terrorist act”.
“A terrorist attack aimed at destroying Russia's critical civilian infrastructure,” he said. “It is obvious that the Ukrainian secret services ordered, organised and carried out the terrorist attack aimed at destroying Russia's critical civilian infrastructure.”
“A number of terrorist attacks and attempts at similar crimes have been committed against our country's electric power facilities and gas transportation infrastructure, including an attempt to undermine one of the sections of the TurkStream gas transmission system.
“All this is proved by objective data, including testimony by the detained perpetrators of these terrorist attacks themselves.
“If attempts to carry out terrorist attacks on our territory continue, Russia's responses will be harsh … No one should have any doubts about this.”
Orysia Lutsevych, a Ukraine military specialist at the Chatham House think tank, suggested that the bridge attack meant it was now a “real problem for the Russians to resupply their forces in the south”.
She also said that the bridge blast could be prelude to a broader attack on Crimea, which was annexed by Russia in 2014. “Ukraine could be planning to target Crimea in a serious way and they are preparing the military campaign in Crimea,” she told The National. “This could be part of the same preparation.”
Sam Cranny-Evans, of the Rusi think tank, said the damage to the bridge would have an impact on getting logistics into the key front-line positions in the Kherson region, but was “not the deciding factor” for the war’s outcome.
“The deciding factor is can Russia transform its army in the next five weeks with its current mobilisation and can they survive winter?”
The attack was a severe blow to the “credibility of Russian military and FSB intelligence services,” said former Brig Ben Barry, a military analyst at the IISS think tank.
“It will also be very unsettling to the Russian defenders of Crimea, especially those dependent on it as a supply route, including forces in Kherson and Zaporizhzhia, and to the local population and local pro-Russian politicians.”
He added that it was now likely that Ukraine would mount “more deep strikes” using special forces, drones and artillery in the coming months.
“We can also expect Ukrainians to mount probing attacks, which if they succeed, they'll exploit and continue to push the Russians back.”