At a conference on piracy in Singapore, the International Maritime Bureau said China failed to prosecute pirates, and gave the impression it was encouraging them to hijack vessels.
Captain Jayant Abhyankar, IMB's deputy director, said that countries have a responsibility to arrest and charge pirates in terms of their own laws.
"Countries like China are signatories to the Rome convention which obliges countries to try the pirates under their own laws. It is a great pity that having caught these pirates, they allow them to go back home without charge," he said.
Attacks more violent
The Singapore conference was set up by the International Maritime Organisation in an attempt to tackle the problem of pirate attacks, which are becoming more violent.
East Asia is the area worst affected, with 67 being killed in pirate attacks last year, and hundreds taken hostage.
Delegates at the conference blame the Asian economic crisis for making the piracy problem more severe.
They say that pirates are now well-organised, chose their targets carefully and can make millions of dollars from their activities.
There were fewer attacks during 1998 than in 1997 as shipping companies took greater precautions, but the attacks became more violent, the conference was told.
The seminar, involving officials from 10 countries, will discuss co-operation agreements between neighbouring countries to combat the problem, as well as looking at the legal implications of allowing warships to confront pirates in international or territorial waters.
Experts say that despite the rise in violent attacks, few of the pirates end up behind bars and in some countries that is simply because it is often unclear who is responsible for investigating crimes at sea.
Ecological disaster feared
Oil tankers are among the craft targeted by pirates, who have been known to siphon thousands of litres of oil into another vessel. Hijacked tankers have been left to sail on with navigation systems vandalised and the crew murdered or tied up, prompting fears of a major collision or ecological disaster.
The waters off Indonesia, one of the countries worst affected by the regional economic downturn, saw 59 of the nearly 200 reported attacks last year.
Many of those were attributed to desperate people targeting any vessels that they believed were carrying food.
Other countries whose territorial waters had high levels of piracy were:
Among the recent piracy cases reported to the conference were:
Country profiles
International Maritime Organisation
UK Department of Transport: Guidelines on piracy
International Maritime Bureau
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