A suicide bomber struck a Shia mosque in Yemen's rebel-held capital on Thursday in an attack that killed at least 25 people during holiday prayers.
The Islamic State in Iraq and the Levant (ISIL) claimed responsibility for the attack, which also left dozens of people injured. Sanaa has been shaken in recent months by a string of ISIL bombings, usually targeting Shias.
Iran-backed Shia Houthi rebels, considered heretics by the Sunnis of ISIL, 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 previous 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."
ISIL, which controls swathes of territory in Iraq and Syria, has repeatedly targeted Shias in Yemen's capital and elsewhere. In the worst attack on March 21, the group bombed several Shia mosques in Sanaa, killing 142 people.
The Houthis seized the capital of Sunni-majority Yemen in September last year and have expanded their grip to other parts of the country.
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 southern port city of Aden.
After six months in exile in neighboring Saudi Arabia, President Abed Rabbo Mansour Hadi returned to Aden on Tuesday with a vow to liberate the country from the Houthis. In a speech to mark Eid al-Adha, Hadi said the Houthis 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 Houthis 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 Houthi fighters swept unopposed into the capital.
ISIL and the Yemen-based branch of its 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 armed group in Yemen, located next to oil-flush Saudi Arabia and key shipping lanes, but experts say ISIL 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 ISIL'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 network's most dangerous branch.