Suicide bombings at two mosques attended by Shiite worshippers including Huthi militiamen in Yemen's capital Sanaa on Friday, and claimed by Islamic State jihadists, killed 142 people, a medical official said.

At least 351 people were wounded, health ministry official Nashwan al-Atab also told AFP, saying that an earlier toll surged following information gathered from various hospitals in Sanaa.

One suicide bomber struck inside Badr mosque in southern Sanaa while another targeted worshippers as they fled outside, witnesses said.

The third suicide bomber targeted Al-Hashahush mosque in northern Sanaa.

Nashwan al-Atab, a member of the health ministry's operations committee, told AFP that 77 people were killed and 30 of the wounded were in critical condition.

The Huthi militia's Al-Massira television said hospitals in the capital had made urgent appeals for blood donations.

Leading Huthi cleric Al-Murtada bin Zayd al-Muhatwari, the imam of the Badr mosque, was among those killed, a medical source said.

Footage aired by Al-Massira showed bodies lying in pools of blood outside the mosques, as worshippers rushed the wounded to hospitals in pick-up trucks.

Another suicide bomber blew himself up outside a mosque in the northern Huthi stronghold of Saada, a source close to the militia said. 

Only the assailant was killed in that explosion and tight security at the mosque prevented the bomber from going inside, the source added.

The Huthis overran Sanaa in September and have since tightened their grip on power.

Their attempts to extend their control into other areas have been met by deadly resistance from Sunni tribes and Al-Qaeda.

Yemen's top security body blamed Al-Qaeda for a car bomb in January that killed 40 people and wounded dozens more at a police academy in Sanaa as recruits lined up to register.

But a leader of the jihadist network denied responsibility at the time.

IS claims responsibility

The Islamic State jihadist group has claimed responsibility for the attack.

In an online statement, the previously unknown Sanaa branch of IS warned that the bombings were "just the tip of the iceberg".

‘Infidel Huthis should know that the soldiers of the Islamic State will not rest until they eradicate them... and cut off the arm of the Safavid (Iranian) plan in Yemen,’ the statement from the Sunni Muslim extremist group said.

Shiite Huthis, who overran Sanaa in September, are accused of receiving support from Iran. 

The statement claimed responsibility for bombings that targeted two mosques in Sanaa and another in the Huthis' Saada stronghold, where an assailant detonated his explosives belt outside a mosque after failing to get in.

It is the first time that IS has claimed any attacks in Yemen where Al-Qaeda remains the most prominent jihadist group.

Al-Qaeda in the Arabian Peninsula, considered by Washington to be the deadliest affiliate of the global jihadist network, remains strongly active in Yemen.