Yemen's prime minister has accused the UK of "war crimes" after munitions reported to be manufactured by Britain struck the war-torn nation.
The Foreign Office is "urgently seeking" more information after Sky News claimed a UK-manufactured cruise missile was used in a raid by Saudi Arabia-led forces.
Locals also shared pictures with the broadcaster of illegal cluster bombs, which experts said had been made in Britain.
The prime minister of the rebel Houthi government, Abdel-Aziz bin Habtour, said the UK Government had profited from the humanitarian crisis by selling arms.
He told the broadcaster: "They have sold cluster bombs to Saudi Arabia.
"They know the Saudis are going to drop them on Yemen ... in Sa'adah and in Sana'a and other provinces.
"I don't think they are guilty of war crimes, I believe so. They are participating in the bombing of Yemen people."
The nose cone of the Storm Shadow cruise missile, which the Ministry of Defence calls "the most advanced weapon of its kind in the world", was reportedly found in the city of Sa'adah and was marked with a UK label.
A Foreign Office spokeswoman said: "We are urgently seeking further information on these allegations. We will not be providing any further comment until more details are available."
Because of their extraordinary risk to civilians, cluster bombs were banned in 2010 in an international treaty signed by Britain.
The latest claims, which came as the US announced it was limiting arms sales to Saudi Arabia over concerns of civilian killings, are the most recent in a line of allegations that they had been used them in Yemen.
Foreign Secretary Boris Johnson said earlier this month that the Government was "deeply concerned" that UK munitions may have been used on civilian targets by the Saudi air force.
But he added he did not believe a "threshold has been crossed" to suspend the sales of British arms to Saudi Arabia, which has headed a regional coalition supporting the Yemeni government against the Houthi rebels.