Three men have been charged over a alleged plot to release cyanide gas in the London Underground, say police.
They are believed to be from either Tunisia or Morocco.
Reports say the suspects are part of a muslim fundamentalist group with links to al-Qaida.
Rabah Chekat-Bais, 21, Rabah Kadris, in his mid 30s, and Karim Kadouri, 33, all of no fixed abode, have been charged under Section 57 of the Terrorism Act 2000 for the possession of articles for the preparation, instigation and commission of terrorism acts.
Unemployed Chekat-Bais appeared before London's Bow Street Magistrates Court last Monday and Kadris and Kadouri, also both unemployed, appeared in the court on Tuesday.
All three men were remanded in custody to appear before magistrates again on November 18.
Scotland Yard is refusing to comment on claims in the Sunday Times the attack involved releasing cyanide gas on the Tube network.