Somali lawmakers on Tuesday blocked a bill criminalising piracy which was proposed by the justice minister to pave the way for a local tribunal.

The bill finalised last week by the government is meant to beef up Somalia's legal arsenal in prosecuting and detaining pirates, who have so far been mainly tried abroad.

"We ask lawmakers to endorse this bill against piracy which will help change conditions for many Somali youths who are serving prison terms outside the country," Justice and Religious Affairs Minister Abdullahi Abyan Nur said.

Nur said the law would be a major step in combating piracy, which soared to record levels last year, with sea-jackers dodging an armada of foreign warships to capture dozens of vessels and make hundreds of seamen hostage.

But severals lawmakers challenged the bill during a heated debate in the Somali capital and forced a revision of the document.

"This text on the punishment of pirates is not compatible with Islam and therefore cannot be approved," Mohamed Mohamoud Heyd, a member of parliament, said.

"It isn't necessary either at this point because the pirates are also fighting the foreign ships that are plundering our fish and other marine resources," he added.

Several other MPs voiced the same opinion and the vice president of parliament adjourned the session by instructing a 15-member committee to amend the bill within five days.

Suspected Somali pirates are currently on trial in Kenya and the Seychelles, which have both signed deals with foreign navies for the prosecution of piracy suspects, as well as in several Western countries.