BARCELONA, Spain - Two Spanish aid workers freed by Al-Qaeda's North African offshoot returned home Tuesday after nine months in captivity following the reported payment of a ransom of millions of euros.

The Spanish government expressed delight at the release of Albert Vilalta, 35, and Roque Pascual, 50, who were seized in Mauritania on November 29 along with a third Spaniard, 39-year-old Alicia Gamez, who was freed in March.

But Spanish Prime Minister Jose Luis Rodriguez Zapatero, confirming their release late Monday, made no mention of any payment despite one media report that up to seven million euros (S$12 million) had changed hands.

He said only that the government had "stepped up the activities of its political, diplomatic and intelligence services to secure their release."

Al-Qaeda in the Islamic Maghreb (AQIM) said it had agreed to free the hostages after some of its demands were met, the Spanish newspaper El Pais reported, quoting an audio statement it said was from the group.

These demands included a ransom of several million euros, and the release of the mastermind behind the kidnapping who was jailed in Mauritania and freed in Mali just hours before the hostages' release, according to media reports.

El Mundo newspaper said that the government paid out 6.8 million euros in total to secure the release of the three Spanish aid workers.

It said the kidnappers had demanded 3.8 million euros and Madrid paid the money in January, but only 1.5 million euros eventually reached the kidnappers, with the rest siphoned off by intermediaries, the newspaper said.

The Spanish government then stumped up further payments of three million euros in April and May, 2.3 million of which went to the kidnappers to meet their full demand for a total of 3.8 million euros while intermediaries took a 770,000-euro slice.

One of the hostages, Gamez, was freed in March following the initial payment. Vilalta and Pascual were released after the second sum reached the kidnappers.

The Spanish government strongly denied that a ransom had been paid following the release of Gamez in May but has been silent on the reports of ransom payments since then.

The two men still in captivity were freed on Sunday in Mali and arrived early Tuesday back home in Spain after passing through Burkina Faso.

On his return Vilalta said they were held under "very hard conditions" in the Sahara desert but were not ill-treated and he thanked the Madrid government for working to obtain their release.

"We know that the Spanish government has made a major diplomatic effort with all governments in the region. We are very proud of our government," said Vilalta, who walked with the aid of a crutch due to a leg injury he suffered while held captive.

Pascual also thanked the government for its "patience" and all those who helped in a "very long, very complicated process."

Their release followed the August 16 transfer from Mauritania to Mali of the kidnap mastermind, Malian national Omar Sid'Ahmed Ould Hamma, who had been jailed for 12 years by a Mauritanian court.

A member of his family and a regional mediator said late Monday that Hamma, who has strong ties to AQIM although is not a member of the group, was freed shortly before the hostages were released.

In its statement AQIM said the release of the Spaniards should serve as "a lesson" for the French secret service, referring to a French-Mauritanian raid in Mali last month that failed to rescue a French hostage and in which seven AQIM members were killed.

The two Spaniards were being held by an AQIM cell led by Algeria's Mokhtar Belmokhtar, who paid Hamma to kidnap them.

While Belmokhtar is considered more a businessman than a religious fanatic, he is believed to be under pressure from a radical branch of AQIM led by another Algerian, Abdelhamid Abou Zeid.

Zeid has overseen the deaths of two Western hostages, Briton Edwin Dyer and Frenchman Michel Germaneau. The latter was slain in the aftermath of the Franco-Mauritanian raid to free him, in which seven of Zeid's men were killed.

He is believed to have been demanding the execution of the Spaniards in retaliation for the July 22 military operation.