Massive explosions have ripped through the al-Shabab group's largest headquarters in Somalia's capital Mogadishu, leaving 25 dead and 30 injured.

The simultaneous blasts hit the base in the southern sector of the city on Friday, a senior al-Shabab official told Press TV on condition of anonymity.

Shortly after the explosions, heavy clashes broke out between the fighters and African Union (AU) troops.

Al-Shabab is trying to defeat the interim western-backed government of Sheikh Sharif Sheikh Ahmed.

Somalia has lacked an effective government since the 1991ousting of former dictator Mohamed Siad Barre, paving the way for factional clashes that have defied numerous bids to restore stability.

Separately, at least 22 people have been killed during fresh clashes between local fighters linked to al-Shabab and government forces in the semi-autonomous Somali region of Puntland.

Fighting erupted on Friday, in the mountainous region of Galagala, between fighters loyal to local militant leader Sheikh Mohamed Said Atom and Puntland government forces.

Another 40, most of them soldiers, were also wounded.

Medics at one of the hospitals in Bossaso, the region's commercial city, said 10 Puntland soldiers have been admitted with gunshot wounds.

Last week, at least nine people -- seven fighters and two soldiers -- died in similar clashes.

Puntland, which declared itself as an autonomous state in 1998, enjoys relative peace compared to southern and central Somalia.

The Horn of Africa nation has been embroiled in civil war for years as it has not had a functioning national government since the overthrow of its dictator, Mohamed Siad Barre, in 1991.