Two suicide bombers attacked a mosque in Yemen's capital on Thursday, killing at least 25 people attending prayers at the start of the Eid al Adha holiday.
The blasts in Sana'a hit a mosque run by the Shi'ite Houthi group that seized control of the city a year ago.
There was no immediate claim of responsibility.
Sunni Islamic State rebels who consider Shi'ites to be heretics have carried out multiple attacks in Yemen in recent months, including deadly car bombings in Sana'a.
The militants have complicated an already difficult situation in Yemen, which has been dealing with a conflict between the Houthis and the government of President Abdu Rabu Mansour Hadi, as well as the presence of al-Qaida in the Arabian Peninsula. More than 4,500 people have died in the past year and many more have been left in need of humanitarian aid.
Hadi, who fled Sana'a for the southern port city of Aden and later to Saudi Arabia, returned to Aden on Tuesday after pro-government forces backed by Saudi-led airstrikes pushed the Houthis back from the city.