Putin says response to Ukrainian attacks will be 'severe'

President Vladimir Putin said Monday that Russia's response to any further Ukrainian attacks would be "severe", after Moscow's forces carried out retaliatory missile strikes across Ukraine.

"It was not possible to leave (Ukrainian attacks) unanswered. If attempts at terrorist attacks continue, the response from Russia will be severe and correspond to the level of threat," Putin said at the start of a televised meeting of his security council.

"Let there be no doubt about it," Putin said.

His remarks come after a huge blast on Saturday damaged a key bridge in Crimea, Putin's flagship project and a vital transport link between Russia and the peninsula Moscow annexed in 2014.

In response to the attack, Putin said Russia carried out "a massive strike with high-precision, long-range weapons... on energy, military command and communications facilities in Ukraine".

Russia's defence ministry said in a statement that the series of strikes it fired "have achieved their objectives. All targets have been hit".

Putin also accused Ukraine of launching three attacks on the Kursk nuclear power plant in Russia, about 85 kilometres (53 miles) from the Ukrainian border and of attempting to hit the TurkStream gas pipeline running from Russia to Turkey under the Black Sea.

Ukraine's capital Kyiv was hit by multiple Russian strikes early on Monday -- the first since late June, AFP journalists witnessed.

Russia's former president Dmitry Medvedev said the strikes were only the "first episode" and that Russia's goal should be "the complete dismantling of Ukraine's political regime".

Russia also launched attacks on several other cities across Ukraine, particularly targeting energy infrastructure.

Electricity cuts were reported in several regions, including Ukraine's second city Kharkiv and its surrounding region, plus the northeastern Sumy region, Zhytomyr region in the north and Khmelnitskyi region in the west.