(Updates death toll, adds militants trial)
SANAA, Oct 2 (Reuters) - Security forces on Tuesday stormed a house in south Yemen used by al Qaeda to make bombs, killing three militant leaders, the interior and defence ministries said.
Yemen, a U.S. ally, has been in upheaval since a popular uprising ousted veteran president Ali Abdullah Saleh in February. It has been struggling, with U.S. support, to suppress an Islamist insurgency that could menace nearby top oil exporter Saudi Arabia and sea lanes used to ship crude.
Three militants and two soldiers were killed when army and security forces raided a house in the southern province of Aden at dawn, prompting clashes that went on for almost two hours, the Interior Ministry said.
"A large amount of various explosives was found in most of the rooms, in addition to booby-trapped gas cylinders and cars ready to be used in suicide attacks and weapons including a rocket and explosive belts," the Defence Ministry website quoted a security source as saying.
The house, in the city of Mansoura, was used as a bomb factory and as a headquarters for al Qaeda leaders in Aden to plan for attacks, the source said.
Security forces seized documents and computers containing plans to attack vital establishments in the province including military, security and civil buildings, the source added.
A local security source told Reuters that among those killed was a Somali fighter and that the militant cell was behind several suicide attacks and assassination attempts in Aden over the past few months.
Separately, a Yemeni court sentenced two militants linked to al Qaeda to death on Tuesday after they were found guilty of killing military and security leaders between July and November last year, the state news agency Saba reported.
Yemen, which borders Saudi Arabia and flanks major world shipping channels, is home to al Qaeda in the Arabian Peninsula, a group viewed by Washington as the most dangerous branch of the militant network established by Osama bin Laden.
Washington, which has pursued a campaign of assassination by drone and missile against suspected al Qaeda members, backed a military offensive in May to recapture areas of Abyan province controlled by al Qaeda offshoot Ansar al-Sharia (Partisans of Islamic Law).
But militants have struck back with a series of bombings and killings.
On Saturday, a suicide bomber killed himself and a bystander in south Yemen in an attempt to assassinate a government official who had targeted al Qaeda militants. (Reporting by Mohammed Ghobari in Sanaa; additional reporting by Dhuyazen Mukhashaf in Aden; Writing by Rania El Gamal; Editing by Mark Heinrich)