Suicide bombers in the Yemeni capital Sanaa blew themselves up during Friday prayers at two mosques used by supporters of Shi’ite rebels, killing 126 people and wounding 260, medical sources said, in the country’s deadliest militant attack in years.

Islamic State, an al-Qaeda offshoot that has seized large areas of Iraq and Syria, claimed responsibility for the attacks, in which four bombers wearing explosive belts targeted worshippers in and outside the crowded mosques.

The Sanaa bombings happened as unidentified warplanes attacked the presidential palace in the southern city of Aden for the second day.

Anti-aircraft guns fired on two planes which dropped bombs on an area that includes the residence of President Abd-Rabbu Mansour Hadi. He was unharmed, sources at the presidency said.

Yemen is torn by a power struggle between the Iranian-backed Houthi rebels in the north and Hadi, who have set up a rival power base in the south backed by Sunni-led Gulf Arab states.

The mosques in Sanaa are known to be used mainly by supporters of the Shi’ite Muslim Houthi group, which controls most of northern Yemen, including Sanaa.

The rise to power of the Houthis since September last year has deepened divisions in Yemen’s complex web of political and religious allegiances.

One witness said he heard two successive blasts at one of the mosques, known as the Badr mosque, in a busy neighbourhood in central Sanaa.

“I was going to pray at the mosque then I heard the first explosion, and a second later I heard another one,” the witness said.

Hospitals in Sanaa were overwhelmed by the dead and wounded, appealing for blood donors to help treat the large number of casualties. A Reuters witness at the Badr mosque said he counted at least 25 bloody bodies or corpses lying in the street and inside the building.

One man carried a child in his arms. The Houthi-linked Al-Masirah television channel showed young men in traditional Yemeni clothes carrying lifeless bodies, some dripping with blood, out of the mosque.