Police made a number of arrests in northern Spain in connection with stolen explosives used in the Madrid terrorist attack, officials said Wednesday. Spanish news agencies said six people were arrested.

"We can confirm that several people have been arrested," an Interior Ministry official told The Associated Press. "They are suspected of having connections with the robbery of explosives," he added.

The government has said the alleged Islamic militant cell that staged the attacks traded drugs and cash for 440 pounds of dynamite stolen from a mine in the northern Asturias region.

One of the 14 people in jail for the attacks is a Spaniard who used to work in a mine in Asturias.

Also on Wednesday, Spanish prosecutors asked investigating magistrate Juan del Olmo to seek permission from Italy to question a suspected mastermind of the Madrid train bombings (search) who was arrested in Milan earlier this week, court officials said.

The suspect, identified as Rabei Osman Ahmed and known as Mohammed the Egyptian, is considered by Spanish police as a "key figure" in the terror attacks that killed 191 people and injured more than 2,000.

In a telephone call monitored by Italian police days before the arrest, a transcript of which was published by Spanish newspapers on Wednesday, Osman Ahmed told his roommate: "The Madrid attack was my plan and those who died as martyrs are my very dear friends." Seven suspects blew themselves in an apartment outside Madrid as police moved in to arrest them on April 3.

"The Madrid connection is me. When it happened I wasn't there," part of the transcript read.

Osman Ahmed was arrested Monday night in Milan on an arrest warrant issued by Del Olmo, who is leading the probe into the bombings in Madrid.

Spain will request his extradition on multiple counts of murder and attempted murder.

The arrest was part of raids which also led to the arrests of fifteen people, mostly Palestinian, Jordanian, Moroccan and Egyptian, in Belgium. However, those detained were apparently not involved in the Madrid bombings, Belgian officials said.

Apart from the Madrid probe, Osman Ahmed is also mentioned in a jailing order issued by Spanish Judge Baltasar Garzon on May 18 against an Algerian named Samir Mahdjoub. Mahdjoub was charged with recruiting Islamic extremists for Ansar al-Islam (search), a group linked to Al Qaeda (search), and sending them to terrorism training camps in Iraq, National Court officials said.

Garzon said Osman Ahmed was linked to Mahdjoub, whose brother Abderrazak is in jail in Italy on charges of recruiting militants to carry out suicide attacks against U.S.-led forces in Iraq.