Car bombs killed or injured at least 50 people near mosques and the headquarters of Yemen's dominant Houthi group in Sanaa on Wednesday, in coordinated attacks claimed by a Yemeni group with links to the Islamic State in Iraq and the Levant (ISIL).
The four blasts rocked the capital as Saudi-led forces conducted more air strikes against Houthi military bases across Yemen and Houthi delegates attending peace talks in Switzerland reported the first tentative progress on the second day of a U.N.-sponsored push for a Ramadan truce. The holiday begins Wednesday.
A security official said the attacks struck the Hashush mosque, the Kibsi mosque, the al-Qubah al-Khadra mosque and the political bureau of the Ansarullah movement of the Houthis, who belong to the Zaydi sect of Shia Islam.
"The explosion was so loud I thought it was caused by an air strike," said a man in his 70s named Ali, who had just left a mosque when a bomb went off.
"I returned and found cars burning, people screaming and wounded people all over."
The a group identifying itself as "Islamic State in Yemen" said in a statement posted online it carried out the attacks. Houthi officials were not immediately available to comment on the incident.
"The soldiers of the Islamic State in Yemen, in a wave of military operations as revenge for the Muslims against the Houthi apostates, (detonated) four car bombs near the centers of Houthi apostasy," the statement said.
The attack is the most serious of its kind in Yemen since suicide bombers killed at least 137 worshippers and wounded hundreds during Friday prayers at two mosques in Sanaa on March 20, in attacks also claimed by the group linked to ISIL.
The Houthi-controlled state news agency quoted an official blaming ISIL for the latest bombings. Supporters of Islamic State exchanged celebratory messages on social media.
ISIL has recently stepped up its operations in Yemen, where Al Qaeda in the Arabian Peninsula (AQAP) had long dominated the militant scene.
Yemen's Foreign Minister Reyad Yassin Abdulla told Reuters in Geneva the peace talks had "made no progress."
The Houthis seized Sanaa in September and pressed into the country's center and south, forcing Hadi and his government into exile in Riyadh.
They say they are campaigning against corruption and years of political marginalization.
A coalition of Arab states headed by Saudi Arabia has been bombing the Houthis and their Yemeni army allies since March 26.
Their aim is to restore Hadi to power and head off what they see as Iran's expansion in the region. The Houthis deny receiving military backing from Iran.
More than 2,600 civilians and combatants have been killed since March and a humanitarian crisis is looming as supplies of food, medicine and other goods run short.
Early on Wednesday Abdulla played down the prospects of a quick ceasefire deal, saying his team still wanted the implementation of a U.N. Security Council resolution demanding the Houthis quit cities they have seized since September. He said he did not want a truce merely "for the sake of publicity".
Houthi delegate Ali Imad said: "There was greater openness and acceptance from the U.N. envoy. All these are signs that today we are moving towards building the first step to resolving this crisis."