Saturday, July 30 2005 14:34 Hrs (IST) - World Time -

London: British detectives today (July 30, 2005) were to grill the four suspects of the failed London bomb attacks of 21 July, who have been arrested after armed raids in Britain and Rome, even as police warned that the threat of further terror strikes remain "very real".

Police believe all four 21 July bomb suspects, Yasin Hassan Omar, Muktar Said Ibrahim, Ramzi Mohammed and Osman Hussain, are now in custody following the raids in the largest manhunt in the history of Scotland Yard.

Omar, 24, arrested in Birmingham on Wednesday, is being questioned over a bomb attempt on the Tube near Warren Street.

Ibrahim and Mohammad were arrested yesterday after armed police surrounded flats at Peabody Buildings, in Dalgarno Gardens, north Kensington. Ibrahim, 27, is the number-26 bus bomb suspect and Mohammed is wanted over the failed attempt to bomb a Tube train near Oval station.

The fourth suspect, named as Somali-born UK citizen, Osman Hussain, 27, was arrested in Rome yesterday. Moves are under way to extradite Hussain to Britain from Italy, but it is not yet clear if he will face charges in the country where he was detained.

Detectives are trying to establish if a fifth man they are holding is linked to a device found in west London.

Meanwhile Metropolitan Police Deputy Assistant Commissioner Peter Clarke insisted the public "must not be complacent" in assuming the threat of attacks had disappeared. "The threat remains and is very real," he told reporters.

More raids can be expected, as police continue to collect evidence for possible future trials, he was quoted as saying by BBC.

They also need to understand what kind of support network lay behind the July 7 London bombings that left 56 people dead and the failed July 21 attacks, as also to find whether it still existed.

The as yet unnamed man, arrested in Tavistock Crescent, is said by police to be of "significant interest" in relation to the events of 21 July.

Detectives believe there may have been a fifth would-be bomber on 21 July, after a device was found last Saturday in a rucksack at Little Wormwood Scrubs, near the Peabody estate.

The immediate priority for police was now to establish if there were any further bomb plots and would also want to know if there were any explosives lying around in warehouses and who the detainees knew.

A BBC correspondent said one of the areas they might be looking for is an unconfirmed report that the attacks on London "were actually planned from a cell inside Saudi Arabia." The Saudi authorities are also investigating the possibility, he said.