At least 53 people were killed and more than 200 wounded when three ballistic missiles struck a training camp for Yemeni government forces in the southern province of Shabwa on Monday, the provincial authority said.

The missiles hit al-Alam camp in Jardan district, near the provincial capital Ataq, where new recruits for the internal security forces were undergoing training. The Shabwa authority described the death toll as preliminary and said hospitals were struggling to cope with the wounded.

The Houthis claimed responsibility. Their military spokesman, Yahya Saree, said the group had targeted what he called a Saudi-backed base and warned that any site with a Saudi military presence would remain a target.

Rashad al-Alimi, head of Yemen's Presidential Leadership Council, said the dead were new recruits and promised a firm response. He accused the Houthis of resorting to what he called terrorist attacks when under pressure.

Fahad al-Khalifi, the deputy governor of Shabwa, said hospitals in the province were overwhelmed and the most seriously injured were being transferred to Hadramout and Aden. The provincial authority appealed for blood donations.

The attack is the largest single loss of life since Yemen's civil war reignited in September, when the Houthis pushed south along the Red Sea coast towards the Bab al-Mandab shipping route. Government forces backed by Saudi Arabia have since launched a counteroffensive.