UK Foreign Office minister Mark Field has promised to get to the bottom of “very serious and well sourced” allegations that British special forces have been training child soldiers in the Saudi-led war against Yemen.

He was answering an urgent question asked in the Commons on Tuesday by the shadow foreign secretary, Emily Thornberry, who suggested the British troops may have been witnesses to war crimes.

She claimed as many as 40 percent of the soldiers in the Saudi coalition were children, a breach of international humanitarian law.

Field also said he would be making inquiries with the UK Ministry of Defence in light of a report that British Special Air Service (SAS) soldiers were injured in a firefight with the Houthi Ansarullah movement in Yemen.

The UK government has a general policy of not discussing the operations of its special forces but Field seemed determined to provide an explanation to members of Parliament.

There had been social media reports from Yemen in February suggesting that British soldiers had been injured in a firefight, and the Daily Express newspaper claimed two SAS members had been injured during a “humanitarian” operation.

However, it was claimed in The Mail on Sunday, a weekly newspaper, that UK special forces were not just involved in so-called humanitarian operations, but providing mentoring teams inside Yemen, including medics, translators and forward air controllers, whose job is to request air support from the Saudis. It claimed five special forces soldiers have been injured.

Conservative Party MP Andrew Mitchell said the allegations were so serious because they flew in the face of successive assurances given by ministers that the UK was not a participant in the Saudi war against Yemen, and was only providing general logistical support to Riyadh.

“These serious allegations that are authoritative and credible, and fly in the face of assurances that have been given from the despatch box on countless occasions,” Mitchell told the Commons.

The UK is known to be close to the Saudi military but denies it is involved in operations against the Houthis in Yemen.

A number of Western countries, the US and Britain in particular, are accused of being complicit in the ongoing aggression in Yemen as they supply the Riyadh regime with advanced weapons and military equipment as well as logistical and intelligence assistance.

The Saudi-led war has taken a heavy toll on the country’s infrastructure, destroying hospitals, schools, and factories. The UN has already said that over 22 million Yemenis are in dire need of food, while 8.4 million are threatened by severe hunger.

According to the world body, Yemen is suffering from the most severe famine in more than 100 years.

Saudi Arabia and a number of its regional allies launched the devastating campaign on March 26, 2015, with the aim of bringing a former government to power and crushing the Houthi Ansarullah movement. Riyadh has failed to fulfill its objectives.