Dozens of people have been killed or injured in a blast outside a police college in the Yemeni capital Sanaa, security sources say.
The bomb went off as people queued for a police recruitment drive, police officials said.
Witnesses said the blast was heard across the city and a large plume of smoke was seen, the BBC reported.
Photographs at the scene of the blast showed the wreckage of a vehicle.
In the immediate aftermath of the blast, ambulances transported casualties away from the scene as bodies were seen lying in the street, witnesses said.
No group has so far said it carried out the attack in Sanaa on Wednesday.
However, Islamic militants belonging to al-Qaeda in the Arabian Peninsula (AQAP) have staged an increasing number of bombings and shootings across the country.
Yemen has been plagued by instability since the start of anti-government protests in 2011, which resulted in President Saleh standing down in 2012 after 33 years in power.
Since then ministers have battled a growing al-Qaeda presence, often with the help of US drone strikes.
In November a new cabinet was formed in an effort to defuse mounting political tensions.
The 24-strong administration, headed by Prime Minister-Designate Khalid Bahah, includes Shia Houthi rebels who seized the capital Sanaa in September.
The security forces meanwhile have been fighting AQAP, in November killing one of its senior commanders in what correspondents said was a significant blow for the organisation.
AQAP has vowed to confront Houthi rebels after they overran Sanaa.