In coordinated sweeps, Italian and Belgian police arrested at least 17 suspected Islamic extremists, including an Egyptian who was alleged to have a key role in the March 11 bombings (search) in Madrid, authorities said Tuesday.

Officials at Spain's National Court said Rabei Osman Ahmed (search), a 33-year-old Egyptian, was detained in Milan late Monday and said to be planning further attacks.

A senior Spanish law enforcement official, speaking on condition of anonymity, described him as a "key figure" in the Madrid commuter train bombings that killed 191 people.

Italian Interior Minister Giuseppe Pisanu (search) said Osman Ahmed was "probably among the principal authors" of the Madrid bombings, and that he "was preparing other attacks."

Osman Ahmed was arrested on a warrant issued Monday by Judge Juan del Olmo, the magistrate leading the investigation into the bombings, said the officials at Spain's National Court. They said they would request his extradition on multiple counts of murder and attempted murder.

Osman Ahmed was identified by people living near a decrepit rural cottage where the bombs used in the attack were assembled, the Spanish court officials said. Fingerprints of several key suspects were found in the cottage.

One other suspect was arrested in Italy, while 15 were apprehended in Belgium — including Palestinians, Egyptians, Jordanians and Moroccans, officials said. One other person was held for questioning in Italy, authorities said.

The suspects arrested in Belgium apparently were not involved in the Madrid bombings, but the investigations in Italy and Belgium were closely linked, said Daniel Bernard, a Belgian federal prosecutor.

He said Belgian investigators were tipped off by Italian authorities.

The other man who was arrested in Italy was the landlord of the Egyptian's apartment in Milan and also used to live there. Italian news reports carried by RAI state television and TG5 private television identified him as Yahia Payumi, a 21-year-old Palestinian, and said he was accused of association for international terrorism, a charge introduced in Italy after the Sept. 11 attacks.

Pisanu said in the statement the arrests were aimed at a terrorist group with links to Al Qaeda, but did not identify the group. Authorities in Spain have blamed the Madrid bombings on Islamic militants with possible links to Al Qaeda.

The Spanish Interior Ministry had said as far back as April 4 that Osman Ahmed was a suspect.

Spanish radio station Cadena Ser quoted police as saying he is an expert in explosives and was in Spain last year, but left the country months before the March 11 attacks.

Police said he had close ties with the accused ringleader of the attacks, a Tunisian named Serhane Ben Abdelmajid Fakhet, according to Cadena Ser.

The Spanish government says Fakhet was among seven suspects who blew themselves up April 3 when police tried to storm their apartment outside Madrid.

The March 11 bombs, planted on four commuter trains, also injured more than 2,000 people.

Before Tuesday, 20 people, mostly Moroccans, had been charged in the attacks, including six for mass murder. Of these, 14 are in jail, and the other six are required to report regularly to authorities. Several dozen more people were questioned and released.