Saudi Foreign Minister Adel al-Jubeir (R) attends a joint news conference with his British counterpart Philip Hammond in Riyadh October 28, 2015. REUTERS/Faisal Al Nasser

British troops are helping identify targets for a Saudi-led military campaign in Yemen and haven’t found any “deliberate” breaches of humanitarian law, Foreign Secretary Philip Hammond said Tuesday.

The British government hasn’t disclosed details of the U.K. military involvement.

Hammond told lawmakers in the House of Commons that “I can’t tell you whether it is six people, but we do have a military presence in Saudi Arabia and we are working with the Saudi Arabians to ensure the following of correct procedures to avoid breaches of international humanitarian law.”

“That is to ensure that target sets are correctly identified, that processes are correctly followed to ensure that only targets that are legitimate military targets are struck,” Hammond said.

He said there had been “no evidence of deliberate breach of international humanitarian law.”

Hilary Benn, foreign affairs spokesman for the opposition Labour Party, called for an “immediate review” of British arms exports licenses to Saudi Arabia in the wake of the reported strikes on hospitals.

Hammond said Britain had “a very robust export licensing process.”

Saud Arabia is the world’s biggest buyer of British weapons.