President Vladimir Putin on Wednesday lauded Moscow's nuclear arsenal and warned that he was ready to deploy the weapons if Russia's sovereignty was threatened.

The Kremlin has touted its nuclear prowess throughout its two-year offensive in Ukraine, last month warning Western countries that there was a "real" risk of nuclear catastrophe if they escalated the conflict.

The Kremlin has touted its nuclear prowess throughout its two-year offensive in Ukraine, last month warning Western countries there was a "real" risk of nuclear catastrophe if they escalated the conflict.

Putin's browbeating rhetoric comes just days ahead of elections in Russia that are all but guaranteed to hand him another six years in power and as his military posts gains in Ukraine.

"Our triad, the nuclear triad, it is more modern than any other triad. Only we and the Americans actually have such triads. And we have advanced much more here," Putin said in a wide-ranging interview with state media.

The "triad" refers to Russia's three-pronged arsenal of weapons launched from land, sea and air.

"We are ready to use weapons, including any weapons -- including the weapons you mentioned -- if it is a question of the existence of the Russian state or damage to our sovereignty and independence," Putin added in the interview that aired on Wednesday.

- Strike on Russian oil facilities -

The Russian leader also dismissed recent comments by French leader Emmanuel Macron, who last month declined to rule out putting boots on the ground, a significant shift in rhetoric as Ukraine struggles on the battlefield.

"The fact is that the militaries of Western countries have been present in Ukraine for a long time," the Russian leader claimed, referring to what the Kremlin says are mercenaries.

"But if we talk about official military contingents of foreign countries, I am sure it will not change the situation on the battlefield," he added.

While Macron has doubled down on his remarks, several of Ukraine's allies, including Washington, have distanced themselves from the idea, which stunned many in Europe.

Putin's comments came hours after Kyiv targeted Russia's energy infrastructure and border regions for the second day in a row.

Ukrainian drones attacked three oil refineries hundreds of kilometres from the frontline in the regions of Ryazan, Nizhny Novgorod and Leningrad, a security source told AFP.

"Our task is to deprive the enemy of resources and reduce the flow of oil money and fuel," the source said.

One drone caused a fire and wounded several people when it crashed into an oil refinery in the Ryazan region that lies some 200 kilometres (120 miles) southeast of Moscow, Ryazan regional governor Pavel Malkov wrote on Telegram.

- 'Disrupt' elections -

In the Rostov region bordering Ukraine, air defences downed three drones flying towards the city of Novoshakhtinsk, regional governor Vasily Golubev said.

The day before, Russia said it had repelled a series of brazen cross-border raids by pro-Ukrainian militias, who burst into its territory and claimed to seize control of a village.

Putin said that Ukraine was upping its attacks on Russian territory in order to interfere with upcoming presidential elections.

"It's simple. This is all happening against the backdrop of failures on the frontline. They did not achieve any of the goals that they set for themselves last year," Putin said.

"I have no doubt that the main goal is, if not to disrupt the presidential elections in Russia then to somehow interfere with the normal process," he said.

Ukraine has ceded ground to Russian forces in recent months as it faces a myriad of shortages, from artillery to air defences, in part because a $60 billion aid package remains held up in the US Congress.

On Tuesday night, a Russian missile strike in President Volodymyr Zelensky's hometown of Kryvyi Rih left four dead and dozens wounded, an attack the Ukrainian leader warned would not go "unpunished".