At least 121 people were killed and 45 injured in an explosion at an ammunition factory in southern Yemen on Monday, medical sources said.

An ammunition factory blasted in Yemen's southern province of Abyan on Monday, killing 121 people. Official Saba news agency quoted unnamed security sources as saying that al-Qaida militants were responsible for the deadly explosion.

Official Saba news agency quoted unnamed security sources as saying that al-Qaida militants were responsible for the deadly explosion.

The blast took place on Monday morning in Al-Hisn area in Abyan's town of Jaar. The factory was seized on Sunday by suspected al- Qaida militants after police and military withdrew from the town following fierce clashes between the two sides.

The police official told Xinhua on condition of anonymity that al-Qaida militants trapped the factory with time bombs after they looted the plant's equipment and ammunition.

"The terrorist group trapped the plant and withdrew as they thought that the security forces would try to regain control over the plant, but the local residents stormed the factory to loot what have been left," the official said.

The police official also said that a large quantity of gunpowder were taken away by al-Qaida militants, while a witness said about 650 kg of copper for making ammunition have also been seized by al-Qaida group.

The witness told Xinhua that the huge blast might be triggered by a cigarette lit by a resident who stormed the plant on Monday.

Doctors at local Al-Razi hospital told Xinhua that some of the injured people were in critical condition.

Abyan is the stronghold of resurgent al-Qaida in the Arabian Peninsula (AQAP) which have been carried out almost daily operations and string of attacks against the Yemeni security and military personnel, leaving dozens killed since 2009.

Police sources in Abyan have confirmed that the AQAP has taken control of several districts and towns in the southern provinces of Abyan and Shabwa as the security authorities were busy in protecting weeks-long anti-government protests demanding President Ali Abdullah Saleh to resign.