A car bomber targeted a police enrollment at a college in Sanaa, Yemen on Wednesday, killing at least 30, security officials said.
Dozens of people were wounded, and the death toll could rise further, according to Al Jazeera.
The blast could be heard across the Yemeni capital and a large plume of smoke could be seen, according to Al Jazeera. In the aftermath, prone bodies were left lying amid twisted debris and recruits' discarded documents on the street, reports said.
Eyewitness Jamil al-Khaleedi told the Associated Press: "What happened is we were all gathering and ... (the bomber) exploded right next to all of the police college classmates. It went off among all of them, and they flew through the air."
No one has yet taken responsibility for the attack, but al-Qaeda in the Arabian Peninsula has targeted security forces several times in the past, the BBC said.
Yemen has been the scene of instability since anti-government protests in 2011 caused the downfall of strongman President Abdullah Saleh after 33 years in power in 2012.
Late last year, rebels from the Houthi group seized large portions of the country, including a number of government buildings in Sanaa.
Days of heavy fighting between the Houthis and government forces ended with a fragile peace agreement between the group and President Abd Rabu Mansur Hadi, but tensions between the rival factions in the country remain.