ADEN — A suicide bomber Sunday detonated a truck packed with explosives at an army camp in Aden, killing nine soldiers, a military source said, amid raging battles between troops and Islamist militants.

The defence ministry blamed Al-Qaeda for the massive blast, which soldiers said tore through military vehicles as they were leaving the army camp.

The military source said that nine people were killed and 21 others wounded in the blast, and that some of the wounded were in serious condition, including four who were evacuated by helicopter to the capital Sanaa.

A text message from the defence ministry's news service received by AFP said that the bomber was from Al-Qaeda, but put the toll at four killed rather than nine.

The attack comes just days after another bombing in Aden, the main city in southern Yemen, in which British marine surveyor David Mockett was killed. A Yemeni intelligence officer said that bombing carried "the fingerprints of Al-Qaeda."

Yemen's volatile south has been wracked by fighting between troops and Islamist militants suspected of ties to Al-Qaeda, with at least 12 soldiers killed in the past week alone at Zinjibar, capital of Abyan province, northwest of Aden.

Those killings came after Ayad al-Shabwani, a leader of the Yemen-based Al-Qaeda in the Arabian Peninsula, or AQAP, died during fighting near Zinjibar on Tuesday, a military official said, adding that dozens of soldiers had been wounded.

Soldiers told AFP that Sunday's blast occurred as troops prepared to leave the army camp for Abyan province.

One soldier said the attack was by a suicide bomber whose pickup truck exploded as two personnel carriers were exiting the facility, with the first military vehicle bearing the full brunt of the blast.

Another soldier said that troops were preparing to leave for Abyan when the vehicle had come "in front of the gate of the camp, and then there was a huge explosion".

A lieutenant colonel was among those killed, according to a medic.

Militants belonging to a group called the "Partisans of Sharia (Islamic law), which has been linked to Al-Qaeda, took over much of Zinjibar, the capital of Abyan province, in May.

Thousands of people have been displaced by fighting in Zinjibar between security forces and the militants.

Yemen's Deputy Information Minister Abdo al-Janadi said on Thursday that the United States had provided logistical support to the Yemen military's 25th Mechanised Brigade, which was until recently besieged by the militants in Zinjibar.

US commanders have repeatedly expressed concern that the jihadists have been taking advantage of a protracted power vacuum in Sanaa to expand their operations.

Since January, protesters have been demanding the ouster of veteran President Ali Abdullah Saleh, in hospital in Saudi Arabia since early June for wounds sustained in a blast at his palace.