Somali pirates are leaving a Basque tuna fishing boat hijacked six weeks ago after agreeing a ransom of $3.5 million, one of the pirates said on Tuesday.

The Alakrana was seized by pirates in the Indian Ocean on Oct. 2 with 36 crew aboard, one of at least 13 ships being held off the Somali coast along with more than 230 crew as hostages.

"Most of our colleagues have left the Spanish ship. We may free it some time today," the pirate, who gave his name as Nor, told Reuters by phone from the pirate haven Haradheere.

"The agreement between us and Spain looks satisfactory and we hope it will finish in safety," he said, as pirates waited for the rest of their friends to come ashore.

No Spanish government spokesman was immediately available for comment.

The was a pause in hijackings during monsoon rains, but the Somali sea gangs have stepped up attacks in the past two months. Attacks off the Seychelles have surged as pirates extend their range to evade navies patrolling off the Horn of Africa.

The multinational naval force operating in the area said on Tuesday that pirates had seized a Virgin-Islands owned chemical tanker with 28 North Korean crew members 180 nautical miles northwest of the Indian Ocean archipelago.

Spanish headache

The European Union naval force said the 22,294 deadweight tonnes tanker, the MV Theresa VIII operated from Singapore, had been heading to the Kenyan port of Mombasa but had turned around and was now heading north.

Pirates in the Somali town of Haradheere confirmed they had hijacked the vessel on Monday.

Signs that the Alakrana may be released soon will come as a relief to Spain. Previously, the pirates had said the vessel would not be freed unless two suspected Somali gunmen captured by the Spanish navy near the tuna ship were freed.

On Monday, a court in Madrid charged the two Somalis with armed robbery and kidnapping.

A member of the Alakrana''s crew told Spanish radio by telephone from the ship earlier on Tuesday that he expected the affair to be over quickly.

Asked about a report in the Spanish newspaper El Mundo that the pirates would free the Alakrana within two days, Ricardo Blach said: "I suppose it will be before that." Blach, who said 63 pirates were on board, declined to comment on details of the El Mundo report, which cited a pirate as saying a ransom was about to be paid by Spanish authorities.