A group claiming to be a Yemeni branch of the Islamic State group said it carried out the attack and warned of an “upcoming flood” of attacks against the rebels, known as Houthis, who have taken over the capital and much of Yemen.
If the claims are true, the bombing would be the first major attack by IS supporters in Yemen and an ominous sign that the influence of the group that holds much of Iraq and Syria has spread to this chaotic nation, where a powerful wing of the rival militant group al-Qaeda already operates.
The claim was posted on the same website in which the Islamic State affiliate in Libya claimed responsibility for Wednesday’s deadly attack on a museum in Tunisia.
The rebel Houthis have controlled the capital since September and have been locked in battle with Sunni al-Qaeda fighters in various parts of the country. An official with al-Qaeda in Yemen denied his group was behind the attack.
The four bombers attacked the Badr and al-Hashoosh mosques, across town from each other, during midday prayers, traditionally the most crowded time of the week, according to the state news agency.
Both mosques are controlled by the Shiite Houthis, but they also are frequented by Sunni worshippers.
The rebel-owned Al-Masirah TV channel said the casualty figures had reached 137 dead and 345 injured, and reported that hospitals were urging citizens to donate blood.
It also reported that a fifth suicide bomb attack on another mosque was foiled in the northern city of Saada – a Houthi stronghold.
Scenes from the two mosques showed devastation, with a number of children among the dead. Footage from the al-Hashoosh mosque showed screaming volunteers using bloodied blankets to carry away victims, with a small child among the dead lined up on the mosque floor.
A prominent Shiite cleric, al-Murtada al-Mansouri, and two senior Houthi leaders were killed, the TV channel reported.
Two suicide bombers attacked the Badr mosque. The first bomber was caught by militia guards searching worshippers at the mosque entrance and detonated his device at the outside gates. Amid the ensuing panic, a second bomber was able to enter the mosque and blow himself up in the crowds, according to the official news agency SABA.
Survivors compared the explosions to an earthquake, and said some of those who survived the original blasts were then injured by shattered glass falling from the mosque’s large chandeliers.
Another pair of suicide bombers attacked the al-Hashoosh mosque. One witness said he was thrown two metres by one of the blasts.
Body parts were scattered on the floor of the mosque, said Mohammed al-Ansi, adding, “blood was running like a river.”
Mr Al-Ansi recalled hearing one man screaming, “come back, save the injured!”
Another survivor, Ahmed al-Gabri, said: “I fell on the ground and when I regained consciousness I found myself sleeping on a lake of blood.”