Linking the Red Sea to the Indian Ocean, the blue waters of the Gulf of Aden are one of the most important trading routes in the world. They are also the most feared.

Far from the romantic villains of Hollywood legend, brutal pirates are terrorising congested shipping lanes and oceans from the South China Sea to the Gulf of Guinea. Their targets are not dead men's treasure chests but ships and their crew, who they can hold to ransom, demanding - and getting - sums of up to $1m.

The Gulf of Aden, close to the Somali coastline, is the real piracy hotspot, however, with more than 50 attacks on ships in or near the gulf so far this year, up from just 13 in 2007.

Based on at least three elusive "mother ships" believed to be Russian-made trawlers and a tugboat, bands of pirates fan out in fast, inflatable boats and fire rocket-propelled grenades at their victims. The latest hijack of a retired couple aboard the 50ft yacht Carré d'As (Four Aces) was only foiled when French special forces in night-vision goggles dropped by parachute into waters nearby. The couple were rescued, six pirates were seized and one was shot dead. Extraordinarily, Somali pirates are currently holding hostage 10 other vessels and 221 crew members.

The surge in attacks has come despite a new UN security council resolution allowing naval vessels to enter Somalia's territorial waters and repress piracy "by all necessary means". EU foreign ministers this week agreed to coordinate warship patrols off the Somali coast but the International Maritime Bureau still wants the international community to take "a more proactive approach". French president Nicolas Sarkozy has also hinted other countries are not doing enough. "The world cannot accept this," he declared. "I call on the other countries of the world to assume their responsibilities, as France has done."

Andrew Linnington of the maritime union Nautilus says piracy has got worse because successful demands for large ransoms have inspired "copycat" attacks. Linnington argues that ship owners are not doing enough to protect their vessels and crew and must invest in better alarm systems, CCTV, electric fences on ships and, in some cases, armed guards. It is not just seafarers who are put in peril. Some 3.3m barrels of crude oil - almost 4% of daily global demand - are transported through the Gulf of Aden each day. Linnington warns that if the hijacking of a big oil tanker goes wrong there could be an environmental catastrophe. "It is more by luck than anything else that we haven't had a major disaster yet," he says.