The car bomb detonated on Monday at an army training facility in Aden, killing at least 40 people, according to local officials.
Witnesses said the attacker drove the bomb-laden vehicle into a building used by the Popular Resistance, a local milita fighting Houthi rebels.
A source at a nearby Doctors Without Borders facility reported that at least 15 people were transferred to a hospital immediately following the attack, while noting that the death toll could rise.
Authorities have not said who was behind the incident, although suicide attacks in the country are frequently linked to al-Qaeda or the so-called “Islamic State” (IS) group.
New hopes for Yemen
Last week Kerry visited Saudi Arabia to discuss the ongoing strife in Yemen with both King Salman and Saudi Foreign Minister Adel al-Jubeir.
The US Secretary of State said he and his Saudi colleagues agreed on the need to bring an end to the 18-month-long conflict in Yemen which has killed some 9,000 people and displaced 3 million more.
The allies proposed resuming peace talks with Iran-alligned Houthi rebels, something that is supported by the exiled government. The Houthis took over the country’s capital, Sanaa, in 2014.
The US is actively supporting Saudi Arabia and its allies. Aden, where Monday’s attack occurred, is the temporary base for the Saudi-backed government.