At least 20 people were killed when a suicide bomber struck a demonstration in the heart of the Yemeni capital.
The attack ripped through Sanaa's Tahrir Square, a central plaza currently held by Zaidi Shia rebels. The rally had been called by the Houthis to protest against the president's choice of prime minister, who has now turned down the post.
Al-Qaeda's local offshoot has vowed to fight the Houthis, whose fighters overran the capital last month. A policeman who witnessed the explosion said he saw a man wearing a suicide belt approaching a Houthi checkpoint in Tahrir Square.
"He then exploded amid the security and ordinary people nearby," he told the Reuters news agency.
A photographer working for AFP described seeing the bodies of four children amid the carnage.
Later, at least seven soldiers were killed in a suicide car bomb attack on an army position in the eastern province of Hadramawt.
Nobody has yet claimed responsibility for Thursday's bombings. However, both bear the hallmarks of similar attacks carried out by al-Qaeda in the Arabian Peninsula (AQAP).