Twenty suspected Islamic extremists were arrested across Europe on Tuesday as part of a major anti-terror sweep against cells based in northern Italy that were recruiting would-be suicide bombers to carry out attacks in Iraq and Afghanistan, police said.

The suspects, primarily Tunisians, were wanted on charges ranging from association with the aim of committing international terrorism to falsifying documents to aid illegal immigrants.

"The investigation has revealed recruitment, training and passage to aspiring terrorists to Iraq and Afghanistan," lead investigator Gen. Giampaolo Ganzer, of Italy's paramilitary Carabinieri police, told a news conference.

Eleven suspects were arrested in the northern Italian cities of Milan, Reggio Emilia, Imperia and Bergamo, while nine were arrested on warrants issued elsewhere in Europe, Italian news agencies reported. Authorities in Britain, France and Portugal confirmed arrests.

In Britain, authorities said two suspects were arrested in London and Manchester and face extradition to Italy. The men, identified as Ali Chehidi, 34, and Mohamed Khermiri, 53, were accused of forging documents to help volunteers enter Italy illegally.

Portuguese and French officials each confirmed one arrest, but did not release the suspects' identities.

Portuguese police said they arrested a North African in Porto, about 300 kilometers (190 miles) north of Lisbon, on suspicion of international terrorism, illegal immigration and smuggling. He had been in Portugal for three years and had a Portuguese residence permit allowing travel within Europe's Schengen area.

Police executing the warrants discovered al-Qaida manuals on how to produce explosives, detonation devices and poisons as well as instructions on guerrilla techniques.

Interior Minister Giuliano Amato praised the operation as an example of strong cooperation among European countries.

Italian police said the main cell was based in the northern region of Lombardy, and that intercepted phone calls indicated the roots of militancy in the group dated back as far as 1998. The group also gave indications of its intention to operate long-term, with one member saying: "Things are being done with extreme calm; haste does not bring the desired results," according to a transcript of one call.

"Once more, the central role of Milan and Lombardy in the panorama of Islamic militants has been confirmed," the Carabinieri police said in a statement.

The Lombardy cell had ties with a group in neighboring Emilia-Romagna whose aim is to establish an Islamic state extending from Morocco to China, Italian investigators said.

Intercepted phone calls made clear the aim of sending jihadist fighters to Iraq via Syria, including specific instructions on shaving off beards before departure to give the impression of making a "peaceful trip."

Ganzer said that while the group's main aim was to stage attacks aimed at western targets in Iraq and Afghanistan, they also had ties to groups that planned attacks in Italy.

Police said the Milan-based cell helped a Tunisian involved in planning a failed attack in Bologna flee to France in 2006. The attack was meant to be carried out around Italy's national elections in April 2006, police said.