The troubled Horn of Africa nation has witnessed a surge in attacks as government forces and allied militias wage a declared "all-out" war against the Al-Qaeda-linked militants.

The jihadists stormed the base at Janay Abdale, located around 60 kilometres (40 miles) outside the port town of Kismayo.

Somali army officers said the militants used explosive-laden vehicles to mount an attack on the base before they were repelled.

"We have lost seven soldiers in the fighting," Mohamed Rashed, a local military commander, told AFP by phone.

Another officer Sugow Abdi, who was among the troop reinforcements sent to the base, said several soldiers were killed in heavy combat.

"Fifteen soldiers who were wounded in the attack were taken to the hospital in Kismayo," he told AFP by phone.

Al-Shabaab claimed responsibility for the attack.

Somali forces wrested control of Janay Abdale from the militants in January as part of a ramped-up government offensive against the militants.

Al-Shabaab has been waging a bloody insurgency against the central government in the fragile nation for about 15 years.

In recent months, the army and local militias known as "Macawisley" have retaken chunks of territory in the central Galmudug and Hirshabelle states in an operation backed by US air strikes and an African Union force.

Despite the gains by the pro-government forces, the militants have continued to demonstrate the ability to strike back with lethal force against civilian and military targets.

In the deadliest Al-Shabaab attack since the offensive was launched last year, 121 people were killed in two car bomb explosions at the education ministry in Mogadishu in October.

Although forced out of Mogadishu and other main urban centres more than a decade ago, Al-Shabaab remains entrenched in parts of rural central and southern Somalia.