Russian forces have struck Kyiv with a sophisticated missile and drone attack for the first time in 73 days, officials said.

Air raid warnings blared for hours as Russia targeted eight regions of Ukraine, firing six ballistic and cruise missiles and 90 drones, the Ukrainian air force said.

Air defences downed four missiles and 37 drones, and another 47 drones were stopped by electronic jamming, the statement said. The damage is being assessed.

A firefighter tackles a blaze
It is the first such attack on the capital in months (Ukrainian Emergency Service via AP)

In the past, such combined attacks aimed to overwhelm air defences and cause maximum damage.

The air assault came as it emerged most of the more than 10,000 North Korean troops sent by Pyongyang to help Moscow in the war are engaged in combat in Russia’s Kursk border region, according to the Pentagon.

A Ukrainian army incursion into Kursk three months ago has succeeded in holding a broad area of land and has embarrassed the Kremlin.

Russia’s military has trained the North Korean soldiers in artillery, drone skills and basic infantry operations, including trench clearing, Pentagon deputy spokesperson Vedant Patel said.

Their cooperation faces challenges, according to the Pentagon, including how to achieve military interoperability and overcoming the language barrier.

Kyiv officials say Russia has deployed around 50,000 troops to Kursk in a bid to dislodge the Ukrainians.

Russia has in recent months been assembling forces for a counteroffensive in Kursk, according to the Institute for the Study of War think tank, though the timescale of the operation is not known.

The Kremlin’s plans in Kursk and Ukraine’s efforts to hold back a Russian onslaught in the eastern Donetsk region coincide with political uncertainty over how a US administration under Donald Trump will change Washington’s policy on the war.

American military aid is vital for Ukraine, but Mr Trump has signalled he does not want to keep giving tens of billions of dollars to Kyiv.

US Secretary of State Antony Blinken has said President Joe Biden intends to bolster American military support to Ukraine in the final months of his administration.