Court told how Libyans accused of Lockerbie bombing spent four years planning the attack

The two men accused of destroying Pan Am flight 103 over Lockerbie were agents of the Libyan Intelligence Service who spent four years planning the attack, the Scottish Courtin the Netherlands was toldyesterday.

In an operation that led them from their homes in Malta via the Senegalese capital, Dakar, and the offices of an electronic components factory in Switzerland to special-forces training camps in the Libyan desert, the defendants are alleged to have built, tested and planted the bomb that exploded in the aircraft's hold.

The pair - both said to be Libyan intelligence officers - did so using false passports and aliases; sometimes they travelled in the company of other agents, sometimes alone. Some of the other agents they travelled with were named in court, while others, even now, remain "to the prosecutor unknown".

The details of the complex operation that allegedly caused the destruction of the Boeing 747 and the deaths of 270 people in December 1988 were contained within the first of three indictments put to the two men, Abdelbaset Ali Mohmed Al Megrahi, 48, and Al Amin Khalifa Fhimah, 44, yesterday morning as the trial opened.

"Being members of the Libyan Intelligence Services [LIS]," it was alleged, "you did conspire together and with others to further the purposes of the LIS by criminal means, namely the use of explosive devices in the commission of acts of terrorism directed against nationals and the in-terests of other countries and in particular the destruction of a civil passenger aircraft and the murder of its occupants."

The court was told the conspiracy began in 1985 with the purchase from Mebo, a Swiss electronics company, of 20 electronic timers capable of detonating explosive devices. With other agents the men took the parts to special-forces training camps in the Libyan desert, where they tested them. The men also obtained high-performance plastic explosives and labels that could be used to tag airline baggage. As they were gathering the materials that would allegedly bring down the Maid of the Seas, the men were also setting up a cover story for themselves and their colleagues. In Zurich, Prague and Malta the men set up false businesses - all to be used as cover by LIS officers, the court was told.

There was also a suggestion the men may have done more than just test the equipment. The court heard that in October 1988 - two months before the explosion over Lockerbie - the defendants travelled with other agents to Chad, in central Africa, "for the purpose of carrying out an operation on behalf of ... the LIS".

The following month Mr Megrahi and Mr Fhimah entered the last phase of their plan, sending a fellow agent, Nassr Ashur, to Frankfurt airport - the airport through which the suitcase containing the bomb travelled.

As this was being done the defendants were allegedly making their final preparations. In Malta, where both used the cover of working for Libyan Arab Airlines, they bought clothes and an umbrella and stole luggage tags.

On 21 December 1988, the indictment said, the men placed a suitcase aboard an Air Malta feeder flight leaving Luqa airport, Valletta, for Frankfurt, where it would be transferred via Heathrow towards JFK airport in New York. Inside the suitcase, with clothes and an umbrella, was "an improvised explosive device ... concealed within a Toshiba 'Bombeat' radio cassette player and programmed to be detonated by one of the said electronic timers". This done, Mr Megrahi left Malta for Tripoli, while the unaccompanied suitcase made its way to Frankfurt and then London, where it was placed on flight 103.

The device exploded over Lockerbie, destroying the aircraft and scattering the wreckage. The indictment added: "The 259 passengers and crew and the 11 residents of Lockerbie named in the schedule were killed and you did murder them."

Mr Megrahi and Mr Fhimah each face three charges - conspiracy to murder, murder and contravention of the 1982 Aviation Security Act: they deny all of them. Yesterday the men's lawyers announced they will be using a special defence under Scottish law that will incriminate a number of other people. The court was told these will include members of the Palestinian Popular Struggle Front, including Mohamed Abo Talb, a convicted terrorist and a Crown witness, members of the Popular Front for the Liberation of Palestine-General Command and another Crown witness, Parviz Taheri.