Ukrainian officials said on Thursday that Russia had struck the capital Kyiv with "kamikaze drones" for the first time in an early hours attack, as officials in Ukraine welcomed a Western pledge to deliver air defence systems "as fast as we can" after days of intense missile strikes.

Since Monday, Russia has pummelled Ukraine with missiles, damaging energy facilities nationwide in attacks that Russian President Vladimir Putin said were retaliation for last week's deadly explosion at a Crimean bridge.

That blast ripped through a road and rail link Moscow uses to transport military equipment.

In the early hours of Thursday, Russia struck the Ukrainian capital region with Iranian-made "kamikaze drones", according to an official.

"Another attack by kamikaze drones on critical infrastructure facilities," said Kyrylo Tymoshenko, deputy head of the Ukrainian president's office, without further details.

Earlier, a bombing blitz smashed into the Black Sea port city of Mykolaiv, obliterating the top floors of a five-storey residential building.

A US-led group of around 50 countries held talks at the Nato headquarters in Brussels and vowed to deliver new anti-missile systems to Kyiv.

"The systems will be provided, as fast as we can physically get them there," US Defense Secretary Lloyd Austin said after the meeting, without giving details.

Ukrainian President Volodymyr Zelensky, who has described the Russian missile attacks as an act of terrorism and has pressed the West for an "air shield", welcomed the promised anti-missile systems.

"The more audacious and cruel Russian terror becomes, the more obvious it is to the world that helping Ukraine to protect the sky is one of the most important humanitarian tasks for Europe today," Zelensky said in his daily address to the nation.

Britain on Thursday said it would supply drones and, for the first time, rockets capable of shooting down cruise missiles.

"The AMRAAM rockets... will be provided in the coming weeks for use with the NASAMS air defence systems pledged by the US," the British defence ministry said in a statement.

In an interview, French President Emmanuel Macron also promised air defences.

"We're going to deliver... radars, systems and missiles to protect them from these attacks," Macron said, adding that France was also negotiating to send another six Caesar mobile artillery units. (AFP)