A suicide car bombing at the security headquarters in Yemen's southern city of Aden killed at least three soldiers in what appeared to be an al-Qaeda attack, police have said.
The car exploded as it rammed into the front gate of the Aden security offices at dawn on Tuesday, wounding at least seven men, a police official said.
Another police source told the AFP news agency that two other attackers in an explosives-laden car attempted to ram through the gate after the first bombing, but were stopped by security forces.
The two "terrorist elements" are being questioned, he said. Security sources told Reuters news agency that the men had admitted links with al-Qaeda.
The men tried to force their way into the compound in Aden in several cars, with the bomber blowing himself up in one of the vehicles which was packed with explosives, news agency SABA said.
Two police centres in different parts of the city simultaneously came under attack with rockets, a third source said, adding that there were no casualties.
The attack bore the hallmarks of al-Qaeda in the Arabian Peninsula (AQAP), which earlier this month launched a similar complex assault on the defence ministry complex in the capital Sanaa, killing 56 people, including foreign medical staff.
AQAP took advantage of the weakening of the central government in Sanaa during a 2011 uprising inspired by the Arab Spring, seizing stretches of territory in the south before being driven back in June 2012.
The group is still active in southern and eastern Yemen, and stages frequent attacks on security forces despite Yemeni military operations and US drone strikes.
The group's military chief Qassem al-Rimi apologised for the civilian death toll in the Sanaa attack, saying one of the assailants had disobeyed orders to avoid the medical centre of the complex.
Elsewhere in the country, two explosions late on Monday struck an oil pipeline that pumps about 10,000 barrels per day from the Ayadh fields, in the southern province of Shabwa, to the Nushaima terminal on the Gulf of Aden, a government official said.
The two bombs, planted under the pipeline in different locations, took the conduit out of service, the official added.
Attacks on oil and gas pipelines in Yemen are frequent, and Oil Minister Ahmad Dares said earlier this month that sabotage had cost the country $4.75bn between March 2011 and March 2013.