Nearly 146 people were killed and 345 seriously injured in separate suicide bombing attacks at two mosques in Sanaa on Friday, the latest in recent turmoil that’s rocked the Yemen city due to clashes between Islam’s Sunni and Shia sects.

Four suicide bombers were blown up in the attacks, Fox News reported.

The assaults on the mosques were accompanied by an attack on the presidential palace, various media reported.

Worshippers were inside the Badr and al-Hashoosh mosques for noontime prayers when the suicide bombers detonated their explosives. Nobody’s yet claimed responsibility for attacks, but terror experts say the separate but simultaneous suicide bombings bear all the markings of al-Qaida.

The attacks come just one day after forces loyal to President Abdrabbuh Mansour Hadi clashed with fighters who support Ali Abdullah Saleh, the previous president. Saleh was ousted in 2011 as part of the Arab Spring, but still has a fierce following of dedicated supporters willing to fight for his return.