Yemen's defence minister narrowly escaped assassination when a powerful car bomb ripped through his motorcade as it travelled in the nation's capital, killing at least 13 people in an attack that bore the hallmarks of al-Qaida.

The bombing came a day after Yemeni authorities announced the killing of the No 2 leader of the network's Yemeni branch - the terror group's most active - in an apparent US airstrike, on Tuesday (local time).

There was no immediate claim of responsibility for the midmorning blast in Sanaa, but al-Qaida's Yemeni branch is believed to be behind at least five other failed assassination attempts against the minister, Major General Mohammed Nasser Ahmed, who has recently won national acclaim as a seasoned and popular commander in the fight against al-Qaida militants.

Hours after the attack, Yemen's new president fired the chiefs of national security and military intelligence, as well as the step brother of ousted leader Ali Abdullah Saleh. Ali Saleh al-Ahmar was the director of the office of the supreme commander of the armed forces, a position from which he wielded vast powers.

The bombing appeared to be in the vein of a string of attacks blamed on al-Qaida since the terror network suffered a series of setbacks at the hands of US-backed government troops.

The offensive has dislodged the group from a large swath of southern Yemen it had occupied for more than a year.

The battlefield defeats came as many residents in the south turned against the militants, mostly out of anger over their brutality or because of the disruptions caused by fighting with government forces.

Al-Qaida responded to the defeats by staging brutal attacks that cost them even more local support. In recent months, they have attacked mourners at funerals, targeted troops praying in mosques and sent a suicide bomber to a military parade rehearsal.

Tuesday's bombing hit the last vehicle in Ahmed's three-car convoy as it was travelling through Sanaa's al-Izaa neighbourhood, according to Yemeni security officials. The blast left the car a charred hulk of twisted metal, with burnt bodies strapped inside, and blew out the windows of storefronts and scorched a nearby building. Pools of blood stained the pavement as hundreds of soldiers and onlookers converged on the site.

Eight of the minister's security guards and five civilian bystanders were killed, the officials said on condition of anonymity because they were not authorized to brief the media.

"This is awful," said Mohamed El-Mehdi, who works in the area. "The people and children are unable to grasp what happened." Some of the five civilians killed were the owners of nearby shops, he added.

Al-Qaida's Yemeni branch is seen by Washington as the world's most active, planning and carrying out attacks against targets in both Yemen and the US, including the failed attempt by an al-Qaida operative to detonate an underwear bomb aboard a flight bound for Detroit on Christmas Day 2009.

Earlier this year, nearly 100 Yemeni soldiers were killed and at least 200 wounded when an al-Qaida suicide bomber blew himself up at the parade rehearsal in May. Al-Qaida said at the time it was targeting Ahmed, who was not hurt in the attack.

In September, a suicide attacker driving an explosives-laden car blew himself up in the southern city of Aden next to the minister's passing convoy. Ahmed escaped that attack unscathed as well. There was no claim of responsibility, but Yemen's military was battling al-Qaida militants there at the time.

A month earlier, the minister's convoy also came under attack in the southern province of Abyan, which was an al-Qaida stronghold at the time.

Al-Qaida militants in Yemen took advantage of the political vacuum created during unrest inspired by the Arab Spring last year against long-time authoritarian president Saleh.

As government forces were focused on suppressing protests in the capital and elsewhere, al-Qaida seized control of large swaths of land in southern Yemen, governing several major cities for months until the US-backed offensive led by President Abed Rabbo Mansour Hadi was able to push the militants into hiding.

The killing of al-Qaida in Yemen's No. 2 leader was seen as a major breakthrough for US efforts to cripple al-Qaida in Yemen. The impoverished nation on the southern tip of the Arabian Peninsula is on the doorstep of Saudi Arabia and fellow oil-producing nations of the Gulf and lies on strategic sea routes leading to the Suez Canal.

The operation underlines the heightened cooperation between the US and President Hadi, whose predecessor, Saleh, was long accused by critics of not fighting al-Qaida wholeheartedly, using militants to counter the weight of political opponents and foreign military assistance to bolster military units loyal to him and commanded by members of his family.

- AP