The Alakrana, a Basque tuna fishing boat, is seen from a Spanish navy aircraft while sailing off Somalia's coast on Oct. 3. Spain announced that the boat and its 36-person crew, held by Somalian pirates for six weeks, was freed on Tuesday. (Spain Defense Ministry/Associated Press)

Somalian pirates have freed a Spanish fishing vessel and its crew of 36, Spain's prime minister said Tuesday.

The Spanish tuna trawler Alakrana was hijacked in the Indian Ocean six weeks ago and its crew taken hostage, but Spanish Prime Minister Jose Luis Rodriguez Zapatero said on Tuesday all the crew members are now safe.

The pirates had threatened to kill crew members unless two of their colleagues captured during the hijacking were freed, but Spanish authorities had ruled out returning the captured pirates.

Zapatero did not say whether a ransom had been paid, however.

$3.5M ransom paid, pirates claim

A self-proclaimed pirate and village elder in Somalia said the pirates were paid $3.5 million in ransom to free the ship and crew.

Ali Ahmed Salad says 12 armed pirates who have been holding the ship the last six weeks left it shortly after noon Tuesday and joined colleagues near the town of Harardhere after receiving the ransom.

Somalia, which has not had an effective central government for 18 years, has become the world's piracy hotspot, and the Gulf of Aden off the east coast of Somalia, one of the world's busiest sea lanes, has seen increased pirate activity.

The International Maritime Bureau's piracy reporting centre in Kuala Lumpur said there have been 147 attacks in the Gulf of Aden between January and September of this year.

With files from The Associated Press