Fighting between al-Shabab and government and African Union (AU) troops in the central Hiran region has left 18 people dead on both sides, the Somalian armed group has said.

Al-Shabab spokesman Abdulaziz Abu Musab told the AFP news agency on Saturday that the deaths occurred after the group's fighters attacked a base of the AU force in Buloburde town, about 200km north of the capital Mogadishu.

The casualties could not be immediately confirmed, but the al-Qaeda-linked fighters said the dead included five of their own men.

The government said six al-Shabab members had been killed, but gave no figures of any casualties on their side.

"Nine soldiers with the African Union, four of their Somali counterparts, and five mujahedeen from our Shabab were killed in the fight," Musab said.

The fighting began around midnight Friday, lasting about four hours into Saturday morning, he said. "Our fighters went into the camp, that is where the killing took place," Musab added.

Troops from the 22,000-strong AU force captured Buloburde from al-Shabab earlier in the year, but the armed group controls large parts of the rural area surrounding the town.

Somalia's Information Minister Mustafa Duhulow praised the security forces for repelling waves of attacks by al-Shabab fighters.

"Al-Shabab tried to come back several times in order to take their dead bodies, but they were defeated on all attempts," he said.

Famine warning

The latest fighting came after al-Shabab launched attacks in the heart of Mogadishu, including recent raids on the presidential palace and parliament, in a bid to topple the internationally backed government.

The conflict continues amid growing warnings of a humanitarian crisis in the country, three years after more than 250,000 people, half of them children, died in a devastating famine.

The UN has warned that Somalia is facing a new severe hunger crisis, with more than 350,000 people in the capital in need of food aid and parts of the city facing emergency levels just short of famine.

Al-Shabab, who once controlled most of southern and central Somalia, have been driven out of positions in Mogadishu and Somalia's major towns by the AU soldiers.

The UN-mandated force is widely expected to launch a fresh push in coming weeks to seize the last few major settlements still in Shabab hands in southern Somalia, especially the port of Barawe.

Journalist 'killer' arrested

Also on Saturday, Somalia's government said that a journalist accused of killing colleagues and working for al-Shabab has been arrested in Kenya, and would be extradited to Mogadishu.

Several journalists have been killed in recent years in Somalia, one of the most dangerous countries in the world to work as a reporter.

"As a result of surveillance by the Somali security apparatus, the Kenyan security forces captured Hassan Hanafi Haji, wanted for the killing of a number of Somali journalists and other citizens," Information Minister Duhulow said in a statement.

"It is also alleged that he was also deeply involved in al-Shabab's propaganda machine," Duhulow added, claiming that Hanafi was a "senior" member of al-Shabab.

Al-Shabab, who operate their own radio station and regularly release videos, were previously active on Twitter before their accounts were shut down.