For a brief period last year, it appeared the threat posed by a few thousand pirates off the Horn of Africa was being nullified. Increased policing efforts on land by Somali Government authorities and, more importantly, an international naval force at sea had significantly reduced the number of attacks.

But it has proved a false dawn. In recent times, matters have deteriorated in several ways. Among the victims have been a South African couple, Deborah Calitz - whose brother lives in Auckland - and her partner, who were kidnapped in late October. Pirates are threatening to kill them if a US$10 million ransom is not paid within a fortnight.

The pair's abduction off the coast of southern Tanzania illustrates one aspect of the pirates' new approach. The attention of the world's navies has forced them to broaden the base of their operations, most notably by striking into the wider Indian Ocean.

The millions paid in ransom money have also enabled them and their backers to become far more sophisticated. What began as a local response to illegal fishing and the dumping of toxic waste in Somali waters has evolved into organised crime.

Oil tankers, a hugely valuable and vulnerable target because of the crude on board and the fact they do not carry guns, for fear of igniting fires, have become the pirates' speciality.

There has also been an escalation in aggression. Brutal gangs attracted by the lucrative pickings have shown a willingness to use torture against captives, throw them overboard or use them as human shields. Restraint has disappeared.

This attitude may, in part, be a response to the increased resistance put up by many of their targets. But it could also reflect the ideological impact of al-Shabab, an militant Islamic movement that is sweeping Somalia, much as the Taleban claimed Afghanistan in the 1990s.

In the past few months, Somalia's transitional federal government, a loose-knit coalition that was regarded in the West as the country's last-ditch hope, has ceded what little power it had to al-Shabab. The prospects for Somalia and for control of the pirates are doleful.

Al-Shabab has shown its hand in its dealings with Western aid agencies. It seems out of the question that it would join the international community in efforts to combat the pirates on land or sea, particularly if this involves breaches of Somalia's sovereignty.

This blows the West's long-term strategy out of the water. It had tried to prop up the transitional federal government, in the belief it could restore law and order.

Somalia's lack of effective government for two decades, during which warlords and their militias have held sway, has left its people impoverished and created fertile ground for a Taleban-like regime.

The last major international attempt to bring law and order, in 1992-93, ended with the Blackhawk Down episode. Almost 20 years on, the problems Somalia poses the world are set to become even worse.

With that, the emphasis must fall on greater and more ruthless protection of shipping in one of the world's most important trade routes.

The area of ocean is vast and the challenges for the multinational armada are immense. There may be no choice but to change the rules of engagement.