Terrorist Tube gas plot foiled

Three men have been charged over an alleged plot to carry out a terrorist attack on the London Underground as fears over a direct threat to Britain's security mounted.

Though Scotland Yard confirmed that three men had appeared before Bow Street magistrates, they were not charged with plotting a specific outrage. But reports today claimed that the men had been planning to bring the ingredients for a gas bomb into Britain, most probably to release cyanide into the Tube network.

No chemical or bomb-making equipment was discovered, but the men are being held under Section 57 of the Terrorism Act 2000 for the possession of articles for the preparation, instigation and commission of terrorist acts and are due to appear before magistrates again tomorrow.

The threat to the Underground has also been revealed within days of the re-emergence of Osama bin Laden. In a tape broadcast by the al-Jazeera satellite network, which the US authorities have accepted as almost certainly authentic, the al-Qa'ida leader specifically threatened Britain and five other Western allies of the US. The three suspects are believed to be connected to an Algerian terror network that has close links with al-Qa'ida.

It is understood that six people were originally arrested but only three – Rabah Chekat-Bais, 21, Rabah Kadris, in his mid-30s, and Karim Kadouri, 33, were charged. All three appeared in court on Tuesday, are unemployed and of no fixed address.

According to The Sunday Times, the three north African men were suspected of being al-Qa'ida terrorists whose most likely target was a crowded London commuter train. The Government has rejected suggestions that the arrests on 9 November had prompted Tony Blair's terror warning at the Lord Mayor's Banquet in the City last Monday or a Home Office warning, later withdrawn, that terrorists might resort to using "a so-called dirty bomb or poison gas". MI5 is reported to have been tracking the alleged conspiracy for several weeks, and the Prime Minister must have been aware of the details.

Home Office sources, responding to concerns that the public had not been made aware of any potential threat, said the Government was receiving daily intelligence and that if the Government or the police felt there was a threat, they would have warned people. Last Monday Mr Blair said barely a day went by without new intelligence about a threat to British interests.

A Government source said last night: "The Government will take whatever measures necessary to combat the threat of potential terrorism."

MI5, the security service, is reported to have been monitoring the group for several months but Scotland Yard's anti-terrorist branch was urged to make the arrests before detailed inquiries into their alleged links with al-Qa'ida could be made.

The devastating potential effect of a gas attack on an underground transport system was demonstrated in Tokyo in 1995, when the Aum Shinrikyo cult released sarin nerve gas, killing 12 and injuring 5,000. Members of the cult planted small perforated bags of sarin, designed so that the gas would seep out and spread slowly in the confined spaces of Tokyo's subway during the rush hour.