NAIROBI (AlerNet) - Mogadishu International Airport was considered to be one the safest places in one of the world's most dangerous countries, Somalia, until this month when a suicide bombing killed 17 peacekeepers.

Any illusion of safety evaporated when Islamist al Shabaab extremists in two bomb-laden cars marked as United Nations vehicles gained access to the African Union peacekeeping mission (known as AMISOM) headquarters based at the airport.

The attack, designed to avenge the death of an al-Qaeda militant assassinated during a U.S. commando raid in Somalia, was the grimmest example yet of how the AU mission has become one of the most dangerous and least supported peacekeeping operations in the world.

"Everyone is asking themselves, in just three years, how did a generation of young people become so radicalised that they are willing to blow themselves up at any time?" said Rashid Abdi, an analyst at think tank International Crisis Group (ICG).

"The situation is totally untenable and no one can win this war," warned Abdi.

Already blighted by years of protracted conflict and clan warlordism, Somalia is also now facing its worst drought in nearly 20 years, with half the country's 7 million people in need of international aid.

The use in the attack of U.N. vehicles stolen by the rebels is only likely to make aid delivery even harder in the Horn of Africa country.

DANGEROUS JOB

More than two years after the AU launched its peacekeeeping effort, which is authorised by the United Nations and largely funded by Washington, only 5,000 of the pledged 8,000 troops are on the ground, nearly all from Uganda and Burundi.

Experts say even the full 8,000 would not be enough to help stabilise volatile Somalia.

U.N. missions in the Democratic Republic of Congo and in Darfur in western Sudan each have four times as many troops, even though Somalia is the only operation in Africa where peacekeepers are routinely targeted by insurgents firing mortars, detonating roadside bombs and killing themselves in suicide attacks.

Also, unlike other missions, there is no cease-fire agreement or U.N.-brokered treaty to enforce.

The rebels have refused to enter talks with the transitional government, despite the elevation of the moderate Islamist Sheikh Sharif Ahmed to the presidency.

"AMISOM was a classic setup for failure and ultimately, when push comes to shove, AMISON will have to decide whether it can stay in Mogadishu or leave," said Abdi.

The AU's special representative for Somalia, Nicolas Bwakira, criticised the international community for just paying "lip-service" in its efforts to help solve the Somalia crisis.

Only 20 percent of the pledges made at a donor conference in Brussels earlier this year have been honoured and calls to upgrade the mission's mandate have not been heeded, he added.

The EU's humanitarian chief, Karel de Gucht, warned last week Somalia would become "the new Afghanistan" unless Western nations give its U.N.-backed government the necessary tools to prevent al Qaeda from getting a foothold in Africa.

The AU was swift to say the bombing not shaken its commitment to peace in Somalia but observers say it dampened morale among the peacekeepers and possibly made other African countries wary of contributing troops to the mission.

TOO TIGHT TO WIN THE PEACE

The peacekeeping mission's mandate tightly restricts troops' ability to fight insurgents - it only calls for the AU to protect the government and its institutions, while safeguarding Somalia's civilians is not part of its responsibilities.

The force covers only about one-third of Mogadishu, an area that includes the capital's airport, seaport and a cluster of buildings around the presidential palace that are occupied by the weak, internationally backed government.

Meanwhile, the rebels have tightened their grip on Somalia through calculated violence against civilians, including executions and punishment amputations, and military targets, in particular in Mogadishu, where the government controls little more than a few districts now.

Abdullahi Mohamed Ali, Somalia's security minister who took over after his predecessor was assassinated in a June suicide attack, hopes that government forces will stay motivated to continue their fight against terrorism.

"We want everyone fighting the Somali government to know that they are fighting their brothers and sisters not anyone else," he said.

MAGNET FOR FOREIGN FIGHTERS

Al-Shabaab grew out of a broad Islamist movement that took control of Mogadishu in 2006 before being ousted by Ethiopian troops. Initially its target was Ethiopian troops, as well as the Somali government that invited them in.

But since the Ethiopian pullout earlier this year the insurgents have increasingly been attacking AMISON troops. In March, 11 Burundian soldiers were killed in a double suicide strike by al-Shabaab, among the 34 peacekeepers who have died since the start of the mission in 2007.

What ICG's Abdi describes as globalisation of the Somali conflict continues radicalise the militant group.

"Al-Shabaab sees itself as under attack in the 'global war on terror', which continues to radicalise them," said Abdi.

"That is why Somalia is now a sort of a magnet for foreign fighters from the whole world."

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