A projectile hit a Doctors Without Borders hospital in northern Yemen on Sunday, killing at least four people and injuring 10, the medical-aid group said, the latest in a string of deadly incidents at its facilities in the country.

Doctors Without Borders, also known by its French acronym MSF, said Sunday that the hospital in Razeh, a district of Yemen’s Saada province, was hit at about 9:20 a.m. local time.

The explosion destroyed several buildings in the complex, the group said in a statement, adding that casualties could rise if people are trapped in the rubble.

Doctors Without Borders couldn’t confirm the origin of the attack. It said planes were seen flying over the facility at the time.

A Saudi-led military coalition has been conducting airstrikes in Yemen since March, aiming to unseat Houthi rebels who are backed politically by Iran, Saudi Arabia’s regional rival. Saada province is a Houthi stronghold.