China has executed 13 people in the southern city of Shanwei after one of its biggest piracy trials on record.

The pirates - 12 Chinese and an Indonesian - were convicted of intercepting a cargo ship in November 1998.

They are said to have boarded the Cheung Son masquerading as Chinese police before killing 23 sailors.

They threw the bodies overboard and made off with the ship, selling its furnace slag contents for $300,000.

Another 25 people received long prison sentences.

Skippers warned

The Cheung Son has never been found, says the International Maritime Bureau, which reported earlier this week that the number of raids and attempted raids on yachts and ships worldwide increased by 40%, from 202 to 258, in 1998.

The report said pirates carried guns on 53 occasions and knives were used twice as often as in 1998. Indonesia accounted for 113 of the attacks - almost double its total for 1998.

Armed factions in Somalia, who have held crews from yachts and ships to ransom, have led the IMB to warn skippers to keep at least 50 miles from its coast.

A total of 203 attacks, or more than two-thirds of the incidents, took place in seven countries. After Indonesia, the worst-hit nations were Bangladesh (23), Malaysia (18), India (14), Singapore Straits (13), Somalia (11) and Nigeria (11).