Foreign Secretary Boris Johnson called on Saudi Arabia to carry out an "urgent investigation" into an airstrike on funeral mourners in Yemen.
Mr Johnson said he had spoken to Saudi counterpart Adel al-Jubeir, whose country leads a coalition against Houthi rebels in Yemen.
An airstrike, purportedly carried out by the coalition, left at least 140 dead and over 500 injured in Yemen's capital and rebel-held Sanaa.
ITV News Correspondent reported that coalition planes were seen in the skies as funerals for the mourners took place.
Britain and the US have called for an immediate and unconditional ceasefire to end the raging conflict in Yemen.
As the funerals of 140 people killed in an airstrike in Yemen was held, the attack was met with international condemnation.
One source told me that the Saudis need to hold a full investigation, they need to hold it soon and it needs to be credible.