Piracy at sea fell by a quarter in 2004 though violence rose in the trade-critical Malacca Straits, an ocean crime watchdog said on Monday.
The International Maritime Bureau (IMB) said the number of reported attacks on merchant shipping dropped to 325 versus 445 in 2003.
IMB director Captian Pottengal Mukundan said: "Although the decline in the number of attacks is to be welcomed, there is concern that in some key hot spots the situation has deteriorated."
It said Indonesia remained the world's top piracy black spot. It ranked the Malacca Straits, one of the world's busiest sea lanes, second worst -- despite joint military patrols to deter crime and increase security.
Many of the attacks were serious in the strategic channel with vessels being fired upon and crew kidnapped for ransom.
The narrow strait between Malaysia and Indonesia, with Singapore at its southern entrance, carries more than a quarter of the world's trade and almost all of Japan and China's crucial oil imports.
The agency said the number of mariners killed worldwide increased to 30, up from 21 in 2003. A total of 86 crew were kidnapped with gangs demanding ransoms for their release.
The IMB said oil-producer Nigeria was the most dangerous area in Africa for piracy and armed robbery.
{{/usCountry}}The IMB said oil-producer Nigeria was the most dangerous area in Africa for piracy and armed robbery.
{{/usCountry}}Attacks in Lagos accounted for the highest number in a single port. Nigeria's oil ports and oil tankers were also targeted.
Balikpapan, a major oil port in Indonesia, had the third highest number of attacks reported. A quarter of attacks worldwide were on oil tankers, the IMB said.
Other areas showing a marked increase in attacks included Malaysia, the Singapore Straits, South China Sea and Haiti.
There was a significant drop in the number of attacks in the Philippines, Vietnam, Bangladesh, India, the Caribbean and in the Red Sea and Gulf of Aden.
Bangladesh saw some of the best improvement with only 17 attacks compared with 58 in 2003.