Madrid  - Spain does not intend to cede to the demands of Somali pirates threatening to kill fishermen they are holding as hostages, a senior official said Friday.

The pirates have threatened to kill the fishermen if Madrid refuses to free two of their accomplices.

The two Somalis were captured and flown to Spain two days after the MS Alakrana was hijacked in the Indian Ocean on October 2.

The situation of the two, who have been jailed on judicial orders, was "not negotiable," Secretary of State for Defence Constantino Mendez said.

Mendez said the government did not exclude any options, including a military intervention, to release the 36 fishermen on board the Alakrana. The fishermen include 16 Spaniards, as well as Africans and Asians.

The Basque trawler was seized by a group of 13 pirates on October 2 and taken to near the Somali coast.

Two of the suspected pirates left the vessel on board a skiff. The two, who are known as Abdou Willy and Raagegeesey, were captured by a Spanish frigate taking part in international anti-piracy patrols in the area.

The pirates are now threatening to begin killing the fishermen in groups of three within three days if their companions are not released, the captain of the Alakrana told family members and media over the phone on Thursday.

Three of the Spanish fishermen have already been taken to Harardhere, a Somali port known for the presence of pirates.

The owner of the Alakrana had been close to sealing a deal with the pirates, when they started insisting on the release of Abdou Willy and Raagegeesey, media reported.

The pirates are also believed to have stepped up their financial demands. The daily El Mundo said they were seeking a ransom of 5 million euros (7 million dollars). There were previous reports of a 4-million-dollar demand.

The government has called for calm, saying Somali pirates had never killed their hostages in the past.(dpa)