Enough timers and batteries for 36 bombs were recovered in raids on houses in London on Monday, when seven men were arrested. Forensic science teams continued to search for explosives at addresses in Tooting and Peckham, south London.
Scotland Yard confirmed that officers were searching for explosives intended for bombing public utilities such as gas, water and electricity installations.
The seven men remained in custody under the Prevention of Terrorism Act and were being questioned about the timers.
Police said these and the power units to go with them had been charged up. London and the South-east were only hours away from the start of a potentially devastating campaign.
Commander John Grieve, head of the anti-terrorist squad, said the men would be questioned initially about the plot which the raids disrupted, but they might be questioned later about other matters.
Police have enjoyed a series of successes in uncovering arms and explosive caches in Britain and Ireland over the past few years.
A few days before the IRA's attack on Osnabruck barracks in Germany last month, police in the Irish Republic swooped on a bomb factory on a remote farm in Clonaslee, Co Laois. Semtex, home-made explosives and bomb-making equipment, including timers and batteries, were among the haul.
Earlier this year, the flat in Lewisham, south London, used by Ed O'Brien, whose bomb blew up on a bus, was found to contain 15kg of Semtex, 20 timers, four detonators, an incendiary device and ammunition.
In April last year, police found almost 40 weapons, including sub- machine guns and rifles outside Belfast. They were thought to be for use by loyalists.
That month, Irish police found three mortars, nine detonators and more than 1,000 rounds of ammunition. Officers said the mortars were of the type fired by the IRA.
Also in April, four suspected members of the extreme republican group, the Irish National Liberation Army, including a man once named in court as the organisation's chief of staff, appeared in court charged in connection with the discovery of an arms cache near Dublin.Reuse content