London police have said that they are looking into allegations of war crimes committed by Saudi Arabia in Yemen.

According to the Metropolitan Police’s war crimes team, a “scoping exercise” was underway in order to understand whether Saudi Arabia committed war crimes in Yemen.

“On Thursday, 30 March 2017 the Metropolitan Police Service received a referral of an allegation of war crimes, made against Saudi Arabia committed in Yemen,” a statement from the MPS said.

“Following receipt of the referral, the MPS war crimes team [part of the Counter Terrorism Command] began a scoping exercise and contacted those making the allegations.”

It came as British Prime Minister Theresa May was preparing for a three-day visit to the Middle East, which will also include a visit to Saudi Arabia.

Riyadh is Britain’s leading ally in the region. The UK and US have sent over five billion dollars worth of arms to Saudi Arabia since Riyadh began its deadly attack against Yemen in March 2015.

The Saudi aggression, which was launched in order to restore Yemen’s ex-government to power, has killed more than 12,000 Yemenis, according to reports.

Riyadh has also imposed an aerial and naval blockade on its war-torn neighbor.