A suicide bomber struck a mosque in Yemen's rebel-held capital on Thursday in an attack targeting Shiites that killed at least 25 people and wounded dozens during Eid prayers.
There was no immediate claim of responsibility but Sanaa has been shaken by a string of bombings by the Islamic State (IS) jihadist group in recent months targeting Shiites.
Iran-backed Shiite Huthi rebels, considered heretics by the Sunni extremists of IS, seized control of Sanaa a year ago.
Thursday's blast ripped through the Balili mosque, located near a police academy, where the rebels and their supporters go to pray, according to witnesses.
It came as Muslims marked Eid al-Adha, the Feast of the Sacrifice, the most important holiday of the Islamic calendar.
Witnesses said that after a first blast inside the mosque, a suicide bomber detonated an explosives belt at the entrance as worshippers rushed outside.
The perpetrators hid explosives inside shoes and clothing to get past body searches introduced at the entrance after the other attacks, according to the mosque's head of security, Adnane Khaled.
"We found a shoe bomb and explosives hidden in underwear and abandoned in the toilet," he said, adding that two devices had failed to detonate while a third had exploded inside the shrine, causing panic.
"As the crowd rushed to leave the prayer room, a suicide bomber tried to force his way into the mosque," said Khaled. "He was stopped at the entrance by a security officer and blew himself up."
Blood stains and debris were seen on the floor of the mosque after the blast, while Huthi rebels inspected the damage.
IS, which controls swathes of territory in Iraq and Syria, has repeatedly targeted Shiites in Yemen's capital and elsewhere.
IS bomb attacks targeting several Shiite mosques in Sanaa on March 21 killed 142 people. The group has also claimed attacks on mosques in Kuwait and Saudi Arabia.
The Huthis seized the capital of Sunni-majority Yemen in September last year and have expanded their grip to other parts of the country.
- Extremists exploit chaos -
Pro-government forces backed by air strikes and troops provided by a Saudi-led Arab coalition have recently managed to wrest back some southern provinces, including the second city of Aden.
After six months in exile in neighbouring Saudi Arabia, President Abedrabbo Mansour Hadi returned to Aden on Tuesday with a vow to liberate the country from the Huthis.
In a speech to mark Eid al-Adha, Hadi said the Huthis had "suffered defeat after defeat" and that "Yemen will soon be freed".
The Saudi-led coalition launched air strikes against the rebels on March 26, and began a ground operation in July.
Hadi loyalists began an all-out offensive against the Huthis in the oil-rich Marib province east of Sanaa earlier this month, aiming to retake the capital.
The United Nations says around 5,000 people have been killed and 25,000 wounded, many of them civilians, since late March in Yemen.
Yemen has descended into chaos since the 2012 ouster of longtime strongman Ali Abdullah Saleh, and security has broken down since Huthi militiamen swept unopposed into the capital.
IS and the Yemen-based branch of its jihadist rival Al-Qaeda have exploited the turmoil to boost their activities in the impoverished country on the tip of the Arabian Peninsula.
Al-Qaeda has long been the dominant jihadist force in Yemen, located next to oil-flush Saudi Arabia and key shipping lanes, but experts say IS is seeking to supplant its extremist rival.
Al-Qaeda in the Arabian Peninsula (AQAP) controls parts of the vast southeastern province of Hadramawt, including the provincial capital Mukalla, which it is seized in April.
It has distanced itself from IS's tactics, saying that it avoids targeting mosques to protect "innocent Muslims".
The United States has waged a longstanding drone war against AQAP which it regards as the jihadist network's most dangerous branch.