According to the BBC, he spoke to Ukraine's President Volodymyr Zelensky in a call on Saturday, during which he confirmed he would send the equipment and additional artillery systems, No 10 said.

Downing Street said the move shows "the UK's ambition to intensify support."

The BBC understands the initial commitment is for 14 tanks.

Around 30 AS90s, which are large, self-propelled guns, are also expected to be delivered.

President Zelensky has thanked the UK, saying that the decision to send the tanks "will not only strengthen us on the battlefield, but also send the right signal to other partners".

He said the UK's support was "always strong" and was "now impenetrable".

No 10 said that during the call, Mr Sunak and Mr Zelensky also discussed recent Ukrainian victories, as well as the "need to seize on this moment with an acceleration of global military and diplomatic support".

The announcement comes as a series of missile attacks were reported at various locations across Ukraine - including Kharkiv and Lviv regions in the country's east and west.

Five people are known to have died and at least 15 others were rescued from rubble after a nine-storey block of flats in Dnipro was damaged by one strike.

Mr Sunak said the Challengers, the British Army's main battle tank, would help Kyiv's forces "push Russian troops back".

Built in the late 1990s, the Challenger tank is more than 20 years old, but it will be the most modern tank at Ukraine's disposal. The tanks will provide Ukraine with better protection, and more accurate firepower.

While the donation alone is not considered a game-changer, it is hoped that the UK's move will inspire other countries to donate more modern equipment to help Ukraine.

Jonathan Beale, Defence Correspondent & Jasmine Andersson/BBC News