MOGADISHU - Over the past year, Somali pirates have hijacked everything from luxury yachts to oil tankers, defying foreign navies and holding the world to ransom over one of the planet's busiest trade routes.

What was once a group of disgruntled fishermen has turned into a fearsome organisation which has attacked more than 100 ships this year alone and raked in an estimated 120 million dollars in ransom money.

Somali pirates captured the world's attention when they hijacked a Ukrainian cargo carrying combat tanks in September and a Saudi-owned super-tanker fully laden with two million barrels of crude two months later.

Armed with rifles, grenade-launchers and grapnel hooks, the pirates have wreaked havoc in the Gulf of Aden, where thousands of merchant vessels bottle-neck into the Red Sea each year.

The cost of ransoms, delays and insurance premiums has hit the shipping industry hard, prompting some companies to opt for the longer but safer route around the Cape of Good Hope.

"This unprecedented rise in piracy is threatening the very freedom and safety of maritime trade routes, affecting not only Somalia and the region, but also a large percentage of world trade," the top UN envoy to Somalia, Ahmedou Ould Abdallah, said recently.

The latest high-profile hijackings have jolted the international community into action, with the dispatching of naval forces by the European Union and NATO to bolster already existing operations in the region.

Brussels earlier this month trumpeted its first-ever naval force, dubbed Atalanta, but pirates have demonstrated their ability to adapt to growing surveillance and started shifting their attacks further south and out to sea.

Foreign navies have thwarted some attacks but pirates have hardly been deterred and obstacles remain to an finding an approach that would substantially curtail piracy off the Somali coastline.

In its first mission beyond territorial waters, China also sent two destroyers and one supply ship to join the fleet of foreign navies patrolling the pirate-infested waters.

The number of different countries and jurisdictions involved create many legal complications to effective anti-piracy efforts.

For example, if US naval forces board a Greek-owned Panamanian-flagged ship with a Chinese crew to arrest Somali pirates and transfer them to Kenya, no fewer than six countries are involved.

Piracy "poses an enormous challenge to the international legal system", UN humanitarian coordinator for Somalia, Mark Bowden, said at an international conference on piracy in Nairobi on December 10.

Experts have outlined a programme that would allow naval coalition countries to transfer detained pirates for prosecution in coastal countries such as Kenya, Yemen, Djibouti or Tanzania.

Yet all agree that piracy cannot be effectively tackled without a stronger strategy aimed at restoring law and order ashore.

The UN Security Council adopted a resolution authorising states combating piracy to conduct operations on land in Somalia.

It allows states to "take all necessary measures that are appropriate in Somalia" to suppress "acts of piracy and armed robbery at sea."

Pirates have operated almost unimpeded in the northern breakaway state of Puntland and further south along the coast of Somalia, which has had no functioning institutions for years and is in the throes of an ever-worsening conflict and humanitarian crisis.

The authorities in Puntland have reacted angrily at suggestions they have a hand in piracy and urged the international community to clean up its own act, notably do more to stop illegal fishing in Somalia's waters and offer more aid to rebuild the country's institutions.

With 12 percent of global maritime trade and 30 percent of the world's crude oil sailing through the straits of Bab el Mandeb, the international community is scrambling to find answers.

With four dedicated UN Security Council resolution projects in the space of a few months, naval powers are seeking more freedom to target the pirates offshore and onshore.

Pirate activity was almost totally curbed under the rule of Islamic Courts Union (ICU), who had controlled a large swathe of Somalia for several months with relative peace and prosperity before being ousted late 2006 by Ethiopian troops backing Somalia’s transitional government.

However after the ICU was ousted from power, the waters off Somalia has become among the most dangerous in the world for shipping, and the country has re-descended into chaos.