Britain is trying to verify reports that Russia has used chemical weapons in an attack on the besieged Ukrainian city of Mariupol, London’s top diplomat said.

“Reports that Russian forces may have used chemical agents in an attack on the people of Mariupol. We are working urgently with partners to verify details”, - Foreign Secretary Liz Truss wrote on Twitter.

“Any use of such weapons would be a callous escalation in this conflict and we will hold Putin and his regime to account”.