A suicide bomber driving a minibus killed at least 38 people Wednesday as cadets gathered to enroll at a police academy in the heart of Yemen's capital, Sanaa, authorities said.

No one has claimed responsibility for the attack, though Yemen-based Al-Qaeda in the Arabian Peninsula (AQAP) has carried out similar attacks.

At the scene of the blast, the dead and wounded lay on a sidewalk against a wall. A charred taxi smoked near what remained of the minibus, yards from a gate for the police academy, which is in a residential area of Sanaa.

The bomber struck as lines of cadets waited outside the academy, preparing to enroll, witnesses said.

"We were all gathering and ... [the bomber] exploded right next to all of the police college classmates," eyewitness Jamil al-Khaleedi told The Associated Press. "It went off among all of them, and they flew through the air."

Police sources and residents told Al Jazeera the death toll was at least 38. The head of police in Sanaa, Abdul-Razak al-Moayed, said the bomber killed at least 33 people.

There has been a recent hike in violence in Yemen since Shia rebels took control of the capital and other cities.

The rebels, known as Houthis, are challenging the government of President Abed Rabbo Mansour Hadi, demanding a greater share of power. Critics of the Houthis view them as a proxy for Shia power Iran — a charge the rebels deny.

Tribal leaders and Yemeni officials warn the rising power of the Houthis and the backlash over U.S. drone strikes against AQAP have caused the group to surge in strength and find new recruits. The Houthis' push into largely Sunni regions of central Yemen has pitted the rebels against Sunnis, to the benefit of Sunni Al-Qaeda.

Washington considers AQAP, linked to several failed attacks in the U.S., the most dangerous branch of the network.

Al Jazeera and The Associated Press