Security officials say the blast happened today morning near Sanaa's police academy as the cadets gathered. They say the death toll likely will rise.
They say the suicide bomber drove a minibus and his attack wounded at least 40 people.
No one immediately claimed responsibility for the attack. Yemen's local al-Qaida branch has carried out similar attacks in the past.
The security officials spoke on condition of anonymity as they weren't authorized to brief journalists.
"What happened is 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."
The blast comes as Shiite rebels known as Houthis seized large areas of Yemen, including Sanaa, earlier this year as part of a protracted power struggle with President Abed Rabbo Mansour Hadi. Their critics view them as a proxy for Shiite Iran, charges the rebels deny. Al-Qaida militants have targeted the rebels in bombings in the past.
