NAIROBI (AFP) - Defeating Somalia's Al-Qaeda-linked Al-Shebaab militants and preventing cross-border attacks like the bloody siege at a Nairobi shopping mall will require more than commando strikes alone, analysts say.

Although killing or capturing senior rebel leaders in raids or drone strikes will dent the insurgents, Shebaab can bounce back from such setbacks, thanks to their shadowy command structure.

"Eliminating top-level individuals would be a strategic blow to the organisation, but of course, the problem is in finding them," said one foreign security source who follows the Horn of Africa. "However, it is not a silver bullet alone... It offers a chance to kick them down, but not keep them down."

According to a recent United Nations monitoring report, Shebaab has built up a powerful "Amniyat" secret service that operates in separate cells "with the intention of surviving any kind of dissolution" of the group. In addition, regional Shebaab "franchises", such as Kenya's radical Al-Hijra group thought to have played a key role in last month's Westgate shopping centre attack, have the ability to work with Somali commanders but also on their own when necessary.

It was not known which Shebaab commander was targeted by elite US forces in their Saturday night raid in the southern Somali port of Barawe. The wanted militant - described as a "high-value" Shebaab leader - was not captured, and it was unclear whether he had been killed, but a US official said several members of the group had been slain.

Somali experts suggested it would be unlikely that reclusive Shebaab chief Ahmed Abdi Godane, who carries a US$7 million (S$8.7 million) US bounty on his head, would have been based in as open a place as Barawe.

Some Shebaab leaders are thought to be based in the mountains of Puntland in the far north-east, known to some as "Somalia's Tora Bora" after the mountainous area of Afghanistan where Osama bin Laden hid out following the attacks of Sept 11, 2001.

Negotiation seems doubtful with the Al-Qaeda-linked group, and there seems little sign that the Shebaab, which wants all foreign forces to leave Somalia and has warned Kenya of "rivers of blood", will actually want to talk.

This leaves the focus on a military solution and a long fight for the 17,700-strong UN-mandated African Union force in Somalia (Amisom), which has already been battling Shebaab fighters for almost seven years.

Somalia's Prime Minister Abdi Farah Shirdon said on Sunday that his country's cooperation with foreign powers battling the Shebaab was "not a secret".

"Al-Shebaab is a threat to us and neighbouring countries," he said. "Al-Shebaab is recognised as a terror group by world countries. Therefore, Al-Shebaab is a problem for Somalia, its neighbours and the world."

Massive steps forward have been taken in the past two years after Shebaab fighters fled fixed positions in the capital Mogadishu and the AU seized a string of key towns. But stamping out Shebaab for good is a distant goal.

Initial targets could include a push to link up currently separated AU forces by seizing Barawe, some 180km south of the capital Mogadishu. One of few ports left in Shebaab hands, it offers both a symbolic and a strategic prize.

"Barawe is a target within reach for the Kenyans," said Mr Stig Jarle Hansen, author of Al Shabaab In Somalia.

Kenyan troops in southern Somalia - along with forces from Sierra Leone - could push north from the port of Kismayo, while at the same time Ugandan or Burundian troops could advance south towards the same target. But just taking towns will weaken but not eliminate Shebaab forces, analysts said.

"The notion that insurgency can be defeated by force displays a fundamental misreading of the enemy's strength," said Mr Abdihakim Ainte, an independent analyst.

Amisom itself complains it lacks ground troops and air power, including both transport and attack helicopters, to fully carry out the task.

"We can't expand anymore... The best we can do is consolidating and cleaning up the areas which we're controlling now," Ugandan army chief Edward Wamala Katumba said shortly after the Westgate attack, calling for up to 7,000 more troops.

"The more we stretch, the thinner we become on the ground and the more exposed we are," Mr Katumba told reporters, adding that Shebaab fighters use "the ungoverned space... to perfect their skills of terrorism".

Financial restrictions, including strangling the lucrative charcoal trade to Gulf States that the Shebaab still have interests in, could also tighten the noose on the group. But Mr Cedric Barnes, Horn of Africa project director at the International Crisis Group think tank, suggested that while it could hamper Shebaab's day-to-day operations, it would not stem the possibility of another Westgate-style attack.

"Attacking sources of funding that are quite high profile is not necessarily going to hurt the kind of networks that carried out this kind of attack," Mr Barnes said.

"This sort of funding (for the attack) would be more ring-fenced."