A loud explosion was heard in the Yemeni city of Aden on Thursday evening, residents and a security source told Reuters.
The explosion took place just outside a central prison in the southern port city, they added.
The security source said the explosion happened in an empty area and damaged a wall.
There were no immediate reports of deaths or injuries.
Pictures posted on social media showed a plume of smoke that appeared to rise from area outside the prison.
After Yemen government officials arrived in Aden on Dec. 30 at least 22 people were killed in attacks.
