Ships' captains are being warned that if they make an unscheduled stop or slow down along the coast of Somalia their vessels will almost certainly be boarded by armed militia.

The International Maritime Bureau [IMB] has highlighted the growing danger in its Annual Piracy Report.

It has increased its rating for the risk of attack along the Somali coastline from possibility to certainty.

Countries reporting the most attacks in 2002

Indonesia 103 Bangladesh 32 India 18 Nigeria 14 Malaysia 14

The IMB said there was an increase in the number of incidents of piracy and armed robbery at sea during the past year. There were 370 attacks in 2002 compared with 335 in 2001.

Indonesia reported the highest number of attacks, followed by Bangladesh and then India.

South America has also seen piracy increase off its shores.

Taking action

The IMB's Jayant Abyankar told the BBC's World Business Report that it was almost impossible to quantify the total cost to business of piracy and armed robbery at sea.

"We can quantify in terms of hijacking whereby the losses could be maybe $50m or $60m a year," he said.

Last year 25 ships were hijacked, compared with 16 in 2000.

IMB director P Mukundan described an increase in violence during these incidents and he said "in some parts of the world it is all too easy to unlawfully board a merchant vessel".

He said it was vital that coastal states allocated resources for more effective patrolling of their waters, especially in the current climate of concerns about maritime terrorism.

There have been some successes. Initiatives from the authorities controlling the Malacca Straits - one of the busiest shipping lanes - saw the number of hijackings fall to 16 in 2002, from 75 in 2000.