Somali pirates have freed 26 Asian sailors held captive in a small fishing village for more than four years, an official and a maritime expert said on Saturday.

The sailors - from China, the Philippines, Cambodia, Indonesia, Vietnam and Taiwan - were seized when the Omani-flagged FV Naham 3 was hijacked close to the Seychelles in March 2012.

Their period of captivity is one of the longest among hostages seized by pirates in the Horn of Africa nation.

"We are very pleased to announce the release of the Naham 3 crew early this morning," said John Steed, East Africa region manager for the Oceans Beyond Piracy group.

"The crew is staying overnight in Galkayo. They will arrive in Nairobi at 18.30 local time tomorrow."

He said they were in the hands of authorities in Galmudug, in central Somalia, and would be repatriated on a UN humanitarian flight before being sent back to their home countries. 

Sharp drop in Somali pirate attacks

Mayor Hirsi Yusuf Barre told Reuters news agency the "crew did not say if ransom was paid".

Steed said one member of the crew had died during the hijacking while two succumbed to illness. Among those released, one was being treated for a gunshot wound to the foot and three were diabetic.

The sailors were held in Dabagala near the town of Harardheere, about 400km northeast of the capital Mogadishu.

Harardheere became known as Somalia's main pirate base at the height of the crisis.

The Oceans Beyond Piracy group said the crew were brought ashore by pirates when their ship sank more than a year after its hijacking.

Piracy off Somalia's coast has subsided in the past three years, mainly due to shipping firms hiring private security details and the presence of international warships.

The wave of attacks had cost the world's shipping industry billions of dollars as pirates paralysed shipping lanes, kidnapped hundreds of seafarers and seized vessels more than 2,000km from Somalia's coastline.

Source: Agencies