Al-Qa'ida used war-torn Somalia as a base to plan and launch Mombassa hotel bombing

A year after Al Qa'ida terrorists bombed a Kenyan tourist hotel, a new investigation has highlighted the pivotal role played by Somalia in the attack, and raised fears that a fresh atrocity could be launched from the war-torn country.

Somalia served as a training base, weapons supermarket and hideout for the Al Qa'ida cell that carried out last November's twin attacks near Mombasa, according to UN investigators.

In a report due to come before the UN Security Council next week, the investigators describe how the terrorists used the country as a base - training under cover of a lobster-fishing business, buying Soviet-made missiles locally, and stealing across the Kenyan border in speedboats and traditional wooden boats.

The investigation shows how breaches of a 1992 arms embargo have made Somalia a terrorist haven. The four-man panel says it has information about new weapons consignments believed to be "solely for the purpose of carrying out further terrorist attacks in neighbouring states".

Ancient trading routes, particularly across the Gulf of Aden to Yemen, provide the backbone of Somalia's thriving arms trade. Every month thousands of dhows - traditional wooden boats - cross the pirate-infested waters with cargoes of goats, milk, crates of Coca-Cola and weapons. According to one Somalia analyst, this dispersed smuggling fleet passes literally "under the radar" of American warships patrolling the Gulf in search of Al Qa'ida suspects.

Many weapons end up in the arms market of Mogadishu, a city carved up into zones of control by rival warlords. Recently, Al Qa'ida has joined the list of customers. After the 1998 bombings of US embassies in east Africa, a cell led by the wanted Comoran national Fazul Abdullah Mohamed set up in Kenya and Somalia.

Posing as lobster fishermen, the team first assembled in Mogadishu in November 2001 for "ideological orientation and arms training" with locally purchased guns, according to the UN report. Later "sleeper" agents were sent to Kenya to identify potential targets. When they found them they returned to Mogadishu to buy weapons - the "Strela 2" surface-to-air missiles which narrowly failed to shoot down an Israeli jet departing Mombasa airport last November.

The explosives used in the Paradise hotel bombing, which killed 15 people, may also have been bought in Somalia. Forensic investigators found traces of TNT and plastic explosives on a gas cylinder used by the bombers. Al Qa'ida may be looking to buy more.

The UN team said it learnt of "recent attempts by extremist groups to procure explosives on the Mogadishu arms market, as well as ongoing militia training in the use of explosives".

After the Mombasa attack, the surviving cell members returned to Somalia, where they lived on allowances provided by a Sudanese financial controller. One alleged terrorist, Suleiman Ahmed Hemed, was plucked from Somalia in a joint US-Kenyan "snatch and grab" operation in April. He is currently standing trial with five other Kenyan suspects.

But investigators believe at least four other cell members are still lying low in Somalia. Since 11 September, US Special Forces and spies have engaged in covert operations in an attempt to contain the terrorist threat. Hussein Aideed, a warlord, told investigators he sold 41 surface-to-air missiles to the US last May.

Other Somali sources - unconnected to the report - said there were rumours that the US has paid substantial sums of money to warlords for handing over Al Qa'ida suspects. They said US agents were believed to operate from a house in Bossasso, in the northern breakaway state of Puntland.

The sanctions report highlights the chaos and lawlessness of Somalia, where there has been no central government since the dictator Said Barre was toppled in 1991. The country is awash with counterfeit currency. Local dealers and politicians, pretending to be the president or central bank governor, have had millions of pounds worth of currency printed in Malaysia, Indonesia and even Canada.

One local businessman, Abdinur Ahmed Darman, declared himself president on Al Jazeera television and even opened an email account with the address "somalipresidency@yahoo.com".

A web of warlord-controlled airstrips offers a smuggler's paradise. Planes change their registration numbers mid-flight to confuse what air traffic control exists, and two charter companies have been caught using the livery of UN agencies. Another charter company, Air Bas, is linked to Victor Bout, Africa's most notorious gun-runner. The weapons freeflow is helped by supplies from neighbouring Ethiopia, which is sponsoring some warlords. According to the panel, an AK-47 goes for $190 (£113) in Mogadishu while a 12.7mm machine gun costs up to $10,000.

Peace talks are taking place in Nairobi but hopes for success are not high. In September shouting delegates punched each other during a debate, and one splinter group returned to Somalia to set up a rival peace process.

Ever since the disastrous peacekeeping mission of the early 1990s, the outside world has mostly left Somalia to its own devices. Islamic groups from the Middle East have rushed into the vacuum. Islamic charities have built schools, mosques and hospitals, and many Somalis have abandoned traditional garments for Arabic-style dress.

"On the whole Somalia has been left to fester in this mess. And maybe one day they will be blamed, like the Taliban was, for fostering these groups," said a UN official.

¿ Saudi police killed two militants, suspected of being al-Qa'ida sympathisers, in a shootout at a fortified hideout in Mecca yesterday, and seized a large number of weapons.