Britain may send armoured Land Rovers on a mercy mission to the besieged city of Mariupol, Boris Johnson has said.

       The Prime Minister said the UK was looking at "going up a gear" in its support for Ukraine, including possibly sending the armoured vehicles to help provide humanitarian relief to encircled cities.

       The southern Ukrainian city has been the target of heavy Russian bombardment. Last week, Emmanuel Macron, the French president, said he would speak to Vladimir Putin to organise an "exceptional humanitarian operation" alongside Turkey and Greece to evacuate it.

       It would have marked the first time foreign troops had entered Ukraine since the conflict began, but Mr Macron was told by Putin on Tuesday that the shelling of Mariupol would only cease when Ukrainian troops defending it surrendered.

       A Kremlin statement said: "It was stressed that in order to resolve the difficult humanitarian situation in this city, Ukrainian nationalist militants must stop resisting and lay down their arms.”

       Mr Macron has maintained direct dialogue with Putin since Russian forces invaded Ukraine on Feb 24.

       Asked whether Mr Macron had been speaking to the Russian president for too long, Mr Johnson said the unity of the G7 and Nato should be prioritisedbut the question of "the value of those negotiations is an open one". He added: "My view is that Putin is plainly not to be trusted."

       Mr Johnson also said he did not think the G7 and Nato should be expected to lift sanctions on Russia if a ceasefire was agreed in Ukraine.

       "In my view, we should continue to intensify sanctions with a rolling programme until every single one of his troops is out of Ukraine," he said.