Somalia has the highest piracy risk in the world, the International Maritime Bureau (IMB) has said.

However, piracy attacks in Nigeria were ranked second highest in Africa after Somalia. But, unlike the latter, where the attacks are for ransom and loot, Nigeria's are political and more sophisticated.

"Between January and June 2007 15 attacks on vessels in or near Somali waters were reported. This exceeds the total 10 which occurred in the whole of 2006," a new IMB report says.

"Many of the attacks have occurred well offshore. As a result, IMB recommends that all vessels not calling into Somali ports remain at least 200 miles (320km) from the coast," IMB director, Captain Pottengal Mukundan said.

He added that, in the absence of any effective law enforcement in Somalia, the only forces able to assist vessels under attack are navy forces of the international coalition.

Two weeks ago, and for the first time in the history of piracy along the Somali Coast, there were reports of the killing of a seaman taken hostage in Somalia.

If the murder report is accurate, it would represent a serious escalation in the violence against kidnapped seafarers.

Co-ordinator of the Seafarers Assistance Programme in East Africa, Andrew Mwangura, said hijackers in Nigeria are often better equipped and have greater knowledge of the Nigerian Delta than the military forces deployed to fight them.

He said the increasing cases of piracy and armed attacks on shipping are creating a rising reluctance among shipowners and crews to make voyages to Somali ports. For instance, Kenya's Motaku Shipping Agencies stopped voyages to the country following frequent attacks leaving hundreds of thousands of hunger stricken people without hope of relief aid.

Mv Rozen was the fourth ship belonging to Motaku to be hijacked along the Somalia coast. Mv Semlow was hijacked with World Food Programme (WFP) aid onboard in Somali waters for more than 100 days in 2005. Mv Miltzow was hijacked for 33 hours in October 2005 while unloading WFP food aid at the Somali port of Merca. Mv Torgelow also suffered the same fate.