The first Djiboutian contingent of 100 soldiers landed in Mogadishu Tuesday to join the African Union force battling Al-Qaeda-linked Shebab forces in Somalia, the mission said.

"An advance party consisting of 100 troops ... arrived at Mogadishu airport this afternoon. A further 800 troops will follow in the course of the next week or so to bring the Djiboutian contingent up to strength," a statement said.

The Somali-speaking Djiboutians join 9,800 Burundian and Ugandan soldiers, who have been deployed since 2007 to protect the Western-backed government from the Shebab in the war-shattered capital.

The AU Mission in Somalia (AMISOM) deputy commander Brigadier-General Audace Nduwumunsi said the troops will be based in Al Jazeera IV area in southern Mogadishu.

"Todays initial deployment of the Djiboutian contingent is a great step forward for the AMISOM Force in Mogadishu and for building stability in the country," Nduwumusi said the statement.

Earlier Somali security officer Mohamed Abdirahman, who initially said 200 Djibouti troops arrived in Mogadishu, welcomed the deployment.

"We are desperately in need of military support to eliminate the threat of Al-Shebab," Abdirahman said.

The troops, who marched out of the airplane in combat uniform and carrying rifles, were welcomed at Mogadishu airport by top Somali military officials and AMISOM leaders.

Djibouti, which neighbours the war-torn country to the north, is the latest country to deploy troops to Somalia, as regional states strive to battle the extremist Shebab insurgents who control much of southern Somalia.

The hardline insurgents control large parts of southern Somalia but are facing increasing pressure from regional armies and government forces, with the rebels leaving fixed positions in Mogadishu in favour of guerrilla tactics.

With the arrival of Djiboutian forces, almost every Horn of Africa nation has been drawn into Somalia's two-decade-long conflict.

In October, Kenya sent tanks and troops into southern Somalia to fight the Shebab militia which Nairobi blames for a series of cross-border attacks and kidnappings of foreigners.

Ethiopian soldiers were reported to have crossed into western Somalia last month, although Addis Ababa has denied its forces crossed the border.

Eritrea has been accused of backing the hardline Shebab, although it too denies any involvement in the conflict.

Djibouti's expected full contribution men will bring the AU force up to 10,700. AMISOM has a UN mandate for up to 12,000 troops, but the AU has asked for it to be beefed up to 20,000.

Sierra Leone is also expected to send a force of 850 soldiers next year, while Kenya has offered for its troops already fighting in Somalia to join AMISOM.

AU force commanders have repeatedly called for the strengthening of the mission to oust the hardline militia.

US Defence Secretary Leon Panetta visited Djibouti, home to the only US army base in Africa last week, when he said that efforts to combat terrorism had "moved to key nodes, like Yemen and Somalia."

The Shebab however have already condemned the Djiboutian deployment, warning that the troops will not succeed in their mission to defeat them.

"850 Djiboutian soldiers are ineffective where thousands of Kenyan, Ethiopian, Ugandan, Burundian and US mercenaries have miserably failed," an official Shebab Twitter post read last week.

"Its very dishonourable of Djibouti to side with the enemy and take part in the invasion of our country," another Twitter message read, from Shehab spokesman Sheikh Ali Mohamud Rage.

The Horn of Africa country has been ravaged by a nearly uninterrupted civil war since the 1991 ouster of president Siad Barre sparked vicious bloodletting by rival militias fighting for power.

In the latest move to return stability, Somali leaders in September signed a UN-backed agreement to improve security, adopt a new constitution and hold polls by August 2012 when the life of the current transitional government expires.