Three Moroccans— a Muslim imam and two aides— were arrested and accused of running a "terror school" at a small mosque in central Italy, police said Saturday.

Italian anti-terror police said they found barrels of chemicals and instructions on how to pilot a Boeing 747 in the Ponte Felcino mosque on the outskirts of Perugia, a city known for its Renaissance architecture and idyllic countryside. A fourth suspect was being sought.

"The investigation has shown that, in the Ponte Felcino mosque, there was a continued training for terrorist activity," anti-terror police head Carlo De Stefano said.

"We have discovered and neutralized a real 'terror school,' which was part of a widespread terrorism system made up of small cells that act on their own."

Police identified the imam as 41-year-old Korchi El Mostapha, and his two aides as Mohamed El Jari, 47, and Driss Safika, 46. A fourth Moroccan suspect was believed to be abroad.

All four are suspected of conducting training with the aim of international terrorism, police said.

Police also said in a statement that the suspects had contacts with two members of the Moroccan Islamic Combat group arrested around two years ago in Belgium.

The Islamic group— known by its French acronym, GICM— is believed to have ties to al-Qaeda and has been linked to the 2004 Madrid train bombings and 2003 attacks in Casablanca, Morocco.

It was not immediately clear if thearrested menhad retained attorneys.

The modest mosque, on the ground floor of a residential building painted red, hid chemicals, including acids, nitrates and ferrocyanide, said Claudio Galzerano, head of the international terrorism division within the anti-terror police.

Films and documents downloaded from the Internet at the mosqueincluded information aboutweapons training, instructions on how to prepare poisons and explosives,and how to lay an ambush, reach combat zones safely and send encrypted messages, apolice statement alleged.

Galzerano told the Associated Press that the men are only accused of involvement in training activities, and that no one is accused of preparing for or carrying out attacks.

20 people under investigation

Another 20 people who frequented the mosque were placed under investigation for various charges, including violating Italy's immigration laws, Galzerano said.

The arrests followed a two-year investigation in the city.

An imam at the larger central mosque in Perugia said the Ponte Felcino group did not appear dangerous, Italian news agency ANSA reported.

The news agency said Perugia's Muslim community is estimated at 10,000 in a city of about 150,000.

"Generally, it's a quiet community. A few made some noise over the international situation, but those were just words," the imam, Abdel Qader, told ANSA. "We trust justice. Everything will be verified, and if any (of the suspects) has made a mistake, he will have to pay."

In May, a court cleared a former imam in the northern Italian town of Varese and two others accused of raising money and recruiting extremists for the GICM.