SPANISH police say they have foiled an attempt by Islamic extremists to carry out bomb attacks coinciding with a state visit to Europe by Pervez Musharraf, the president of Pakistan.

It was reported that other European countries, including Britain, had been put on alert by the Spanish for the possibility of terror attacks.

Alfredo Perez Rubalcaba, the Spanish interior minister, said that five homes and a mosque in central Barcelona had been raided and a quantity of bomb-making material had been seized, including four detonators. Twelve Pakistanis and two Indians were arrested on Friday.

Rubalcaba said police acted on a tip-off from “another secret service” and discovered that some of those detained were about to purchase explosives.

The arrests were made just days before a visit to Europe this week by Musharraf. He is due to go to France and the UK and attend the World Economic Forum in Davos, Switzerland.

The minister said that he could not reveal more about the police operation which was continuing but the National Intelligence Centre (CNI), the Spanish secret service, had warned at least four other European countries to prepare for “imminent attacks”.

A source at the CNI told El Pais, the Spanish newspaper, that the countries facing the immediate threat were France, Britain and Portugal.

The same source said police had found triacetone triperoxide in the Barcelona raids. This is a cheap form of explosive used by suicide bombers in the Middle East. It was used by Richard Reid, the thwarted British shoe bomber.

The main concern was that it appeared that an unknown quantity of the explosive had been removed before the raids. “We are facing a well organised group that had moved a stage further than just being radicals,” the minister said.

“We were alerted by another secret service that they were preparing to commit terrorist actions in Spain, specifically Barcelona.”

Although the interior minister would not link the latest arrests with Musharraf’s visit to Europe, secret service sources told El Pais that the new alert coincided with Musharraf's trip.

The source implied that the CNI had specific information on itinerant terrorists heading for the UK, France and Portugal.

A Whitehall security official said, however, that he had no knowledge of any warning from Spain that an attack on Britain was imminent.

Spain was the scene of Europe’s deadliest Islamist attack in March 2004 when four trains were bombed in Madrid, killing 191 commuters and injuring a further 1,800.

Jose Luis Rodriguez Zapatero, the Spanish prime minister, said that the group of “presumed Islamic radicals” had been detained in Barcelona as a result of “important international collaboration”.

Speaking during a bilateral meeting in Portugal, Zapatero said that “extreme prudence” was required regarding “the intentions” of this “group of Islamic radical activists”.

Barcelona and Madrid both have large Pakistani communities mainly involved in running restaurants and shops.

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