The problem worsened in the first months of 2009 despite patrols by foreign navies.
Last week, Somalia's interim government asked for international help to set up a national coastguard to help tackle piracy, and protect fishermen from illegal foreign fishing boats and to prevent dumping of toxic materials.
I'm aware now these acts are wrong in Islamic teachings
Mr Abdullah, a well-known pirate chief in Puntland, says his group is not holding any ships at present and the authorities have agreed to give them amnesty for previous hijackings.
"I see myself as someone who has been saved from bad deeds," he told the BBC's Somali Service.
"I understand the wrong things that I was involved in and I'm aware now these acts are wrong in Islamic teachings.
Mr Abdullah says he has agreed to work with local leaders to get other pirates to give up what can be a lucrative life on the high seas.
"I will advise those who want to go to sea, they must not do it and I hope they will stop it as we have agreed.
"The ones who are holding ships now, I would call them to release them and they ought not to do it again."
Meanwhile, a Nato warship in the Gulf of Aden has intercepted two boats carrying suspected pirates and has disarmed them, AP news agency reports.
A Canadian frigate chased the two boats and eventually boarded them.
Nato says it found a large amount of firearms and rocket-propelled grenades, as well as equipment such as hook ladders.
The suspected pirates were released after the equipment was confiscated.
When first loaded, the map's focus falls on Somalia where most of the pirates are based. Use the arrow icons to scroll left towards Europe and the United States which are both playing a central role in tackling the problem.
Scroll to the right for a story about the Philippines, which supplies many of the world's mariners.
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