Al-Qaeda attacked a Yemeni army headquarters in a heavily patrolled district of Aden on Wednesday, sparking a gun battle that killed 20 people, most of them militants, officials said.

The building targeted is located in the supposedly tightly secured coastal district of Tawahi that hosts intelligence and political police headquarters, a naval base and a presidential residence.

"We have regained control of the situation," an army official told AFP, adding that the fighting went on for several hours.

Ten of the assailants were killed, along with a suicide bomber who detonated his explosives-laden car at an entrance to the base, the official said.

Six soldiers were killed and 14 wounded, while three civilians including a seven-year-old child were also among those who died, the official added.

The militants launched the attack on the northern side of the army headquarters, with some of them climbing a wall into the building as a car was blown up at a western entrance, the sources said.

Reinforcements from the 31st Armoured Brigade stationed in Aden were dispatched to support the troops in Tawahi, a military official said.

No information was immediately available on the overall number of attackers.

- 'Cowardly attack' -

The official Saba news agency quoted a security official as saying the incident was "a suicide terrorist attack by Al-Qaeda".

"The guards at the HQ have foiled this cowardly attack" and government forces were "hunting down the attackers who fled after the assault," the official told Saba.

The brazen attack on such a highly protected area came despite the authorities having stepped up measures in recent weeks to contain a deadly wave of violence rocking the Arabian Peninsula country for years.

On March 8, President Abdrabuh Mansur Hadi replaced interior minister Abdelqader Qahtan for failing to improve the "below-par" performance of the security forces.

Qahtan's successor, Abdo Tareb, ordered the dismissal of three security chiefs for failing to prevent a March 24 attack attributed to Al-Qaeda on an army checkpoint in the southeastern Hadramawt province, in which 20 soldiers were killed.

Wednesday's assault is similar to one carried out by gunmen from Al-Qaeda-affiliated group Ansar al-Sharia on an army headquarters in Hadramawt in September, in which they took hostages and 12 people died.

The army recaptured the facility and freed the hostages after nearly four days of fighting.

In December, Al-Qaeda militants launched a daylight assault on the defence ministry, killing 56 people.

The group has taken advantage of the weakening of the central government since 2011, as a result of a popular uprising that toppled president Ali Abdullah Saleh after 33 years in power.

Washington regards Al-Qaeda in the Arabian Peninsula as the global jihadist network's most dangerous affiliate and has stepped up drone strikes against the group in recent months.