Britain will await the outcome of a Saudi Arabian investigation into an air strike that killed more than 140 people attending a funeral in Yemen before deciding whether to review sales of arms to the desert kingdom, Downing Street has said.
The Saudi-led coalition battling rebels in Yemen has been blamed for the attack, which is also believed to have injured more than 500 people in the capital Sanaa.
The incident has increased pressure on the UK to halt sales of weaponry, including fighter jets and bombs, to the country.
The Campaign Against Arms Trade (CAAT) said the UK has licensed the sale of more than £3.3 billion worth of arms to the Saudi government since the bombing campaign began in March 2015, with BAE Systems last week announcing it was in talks over a new five-year defence co-operation programme between the two countries. CAAT has applied for the licences to be the subject of a judicial review, which is due to be held by the end of February.
The campaign's spokesman Andrew Smith said: "The humanitarian situation in Yemen is dire and getting even worse. Innocent people are dying every day. The UK Government's response has been to continue supporting the Saudi forces that are dropping the bombs, and to sell them even more weapons.
"There can be no more excuses. There are major steps that the UK can take right now that could alleviate the suffering and reduce the chance of further atrocities. If Theresa May and Boris Johnson are serious about peace, then they must stop the arms sales and use their influence to call for an end to the bombardment."
The Saudi military announced on Sunday that it will launch an investigation into "reports about the regrettable and painful bombing" in Sanaa, but made no admission that coalition forces were responsible for the attack.
Asked whether Britain would review its arms sales in the light of the deaths, a Downing Street spokesman said Saudi Arabia was a "close and important ally for Britain".
The spokesman said: "Clearly we need to know exactly what happened at the weekend and we await confirmation as to what exactly took place.
"Until we have a full assessment of the facts on the ground, it would be inappropriate to comment further. Our position on the situation and Saudi military activities in Yemen has not changed.
"We want the Saudis to carry out their investigation. We obviously regularly raise the issue of compliance with international humanitarian law at the highest levels in the Saudi Arabian regime."
Asked whether the Government would rely on the findings of the Saudi investigation alone, the spokesman said: "If information comes from other sources we would take a careful look at it."
The United Nations' humanitarian co-ordinator in Yemen Jamie McGoldrick described the attack as "horrific" and reminded all parties to the conflict that "under international humanitarian law, they are obliged to protect civilians and civilian infrastructures". He called for an immediate investigation into the incident.
UN Secretary-General Ban Ki-moon condemned the bombing in a statement, and said "any deliberate attack against civilians is utterly unacceptable... Those responsible for the attack must be brought to justice."