However, it announced in a later statement that, after further reflection, it had been decided to release their names.
A D-notice was issued asking the media not to publish their photographs or addresses.
The names were given as John Deverell CB, 57; Stephen Rickard, 35; Michael Maltby, 57; John Haynes, 58; Martin Dalton, 37, and Anne James, 42.
The Northern Ireland Office said that no additional information would be provided about their work.
A security source said last night that the nine military casualties were 'a mixture of people permanently working in the intelligence world and general staff officers who do occasional tours in intelligence'.
The military personnel who died were named last night as:
Col Chris Biles, 41, late Devonshire and Dorset Regiment, based at army headquarters; Lt-Col Richard Lawrence Gregory- Smith, 42, (Intelligence Corps) based at army headquarters; Lt- Col John Tobias, 41, (intelligence corps) based at army headquarters; Lt-Col George Victor Williams, 49 (intelligence corps) based at army headquarters; and Major Richard Allen, 34, (Royal Gloucester, Berkshire & Wiltshire Regiment) based at army headquarters.
Major Christopher John Dockerty, 33, (Prince of Wales Own Regiment of Yorkshire) based at headquarters of 8 Infantry Brigade, Londonderry; Major Antony Robert Hornby, 38, (Queen's Lancashire Regiment) based at headquarters 3 Infantry Brigade, Portadown; Major Roy Pugh, 37, (Intelligence Corps) based at army headquarters; and Major Gary Paul Sparks, 33 (Royal Artillery) based at headquarters, 39 Infantry Brigade, Lisburn.
The four RAF crewmen who died were all from RAF Odiham, Hampshire. They were: Flt Lt Richard David Cook, 30, a pilot; Flt Lt Jonathan Paul Tapper, 28, pilot; Master Air Loadmaster (MALM) Graham William Forbes, 36; and Sgt Kevin Andrew Hardie, 30, Air Loadmaster.Reuse content