SANAA, Yemen (AP) — Security officials say gunmen in an unmarked vehicle drove past a sit-in in Taiz, Yemen's second largest city, and opened fire on protesters, killing one.

Activist Shaher Mohammed Saeed says he heard and saw gunshots from a white pick-up truck driving past protest tents in Taiz at dawn Sunday.

Hundreds of protesters there are pushing for sweeping reforms related to the uprising that began last year and ousted the country's longtime leader.

Security officials say they are investigating the attack.

Separately, officials say they arrested five al-Qaida suspects in the southern city of Aden. The raid comes about a week after militants attacked the intelligence headquarters there, killing 21 people.

All security officials spoke on condition of anonymity because they were not authorized to speak to reporters.