Yemeni security forces have defused a bomb planted at the entrance of an intelligence services building in the southern port city of Aden, the defense ministry said.
The bomb was to have been detonated by remote control, the ministry's website quoted a security official as saying late on Sunday.
Yemeni troops regained control last month of several towns in the southern province of Abyan which Islamist militants had seized last year during political upheaval that toppled President Ali Abdullah Saleh.
But a string of attacks and assassination attempts against security officials showed the militants are still capable of carrying out attacks and highlighted the tenuous grip of Yemen's central authorities on the restive south.
The uprising against Saleh split Yemen's military and raised fears in the United States and top oil exporter Saudi Arabia that political chaos would embolden Islamists in Yemen.
Washington and Riyadh have both been the targets of abortive attacks by Yemen's al Qaeda wing and backed a power transfer deal that replaced Saleh with his deputy in February.
Abd-Rabbu Mansour Hadi, Saleh's successor, took office promising to reunify the military and to fight al Qaeda. In May, he launched an offensive with U.S. backing that drove Islamist fighters out of a host of towns in the south.
Since Hadi came to power, Washington has increased "counter-terrorism" activity in Yemen, targeting al Qaeda figures in drone and missile strikes.
Militant group Ansar al-Sharia (Partisans of Islamic Law) threatened to spread the fight across Yemen after it was forced out of Abyan. The Interior Ministry said it had beefed up security in response and warned there could be more attacks on security targets.