MOSCOW - Russian President Vladimir Putin said on Monday that Ukraine had carried out "terrorist acts" against Russia and pledged to react forcefully if they continued.

In televised remarks, Mr Putin said Moscow had launched long-range missile attacks against Ukraine's energy, military and communications infrastructure on Monday in retaliation for an attack on a vital bridge linking Russia to the annexed Crimean peninsula over the weekend.

"It is obvious that the Ukrainian secret services ordered, organised and carried out the terrorist attack aimed at destroying Russia's critical civilian infrastructure," Mr Putin said of the bridge explosion.

Ukrainian officials were exultant after the blast but Kyiv has not claimed responsibility.

"Through its actions, the Kyiv regime has put itself on a par with the most odious of international terrorist groups. It is simply impossible to leave crimes of this kind unanswered," Mr Putin said, in opening remarks at a meeting of his powerful Security Council.

Cities across Ukraine were left without power or water and several people were killed in Russian missile strikes on more than a dozen Ukrainian cities on Monday morning.

Ukrainian Foreign Minister Dmytro Kuleba said: "Putin is a terrorist who talks with missiles."

Mr Putin said Russia would respond "harshly" to any further attacks by Ukraine.

"If attempts continue to carry out terrorist acts on our territory, Russia's responses will be harsh and in their scale will correspond to the level of threats created for the Russian Federation. No one should have any doubt about that," he said.

He also accused Ukraine of attempting to carry out an attack against a nuclear power plant in Russia and against the TurkStream gas pipeline.

He repeated, without providing evidence, his assertion that Ukraine and its Nato backers were behind still-unexplained ruptures to the Nord Stream gas pipelines which run from Russia to Germany under the Baltic Sea.

The strikes across Ukraine on Monday morning have threatened to further escalate the war that has been raging for more than seven months since Russia invaded Ukraine on Feb 24.

Ukrainian President Volodymyr Zelensky said the rush hour attacks appeared to have been deliberately timed to kill people as well as to knock out electricity.

His prime minister said 11 major infrastructure targets were hit in eight regions, leaving swathes of the country with no power, water or heat. REUTERS