The 15-nation Security Council unanimously adopted a resolution urging Libya ''immediately to provide a full and effective response'' to the British and American demand that the two men - Lamen Khalifa Fhimah and Abdel Basset Ali al-Megrahi - be surrendered to stand trial.

The resolution also ordered Libya to co-operate with France's investigation into the bombing of a French-owned UTA airliner over Nigeria in 1989, in which 171 people lost their lives.

Western diplomats said that they would seek selective UN sanctions against Libya ''in a matter of weeks'' if the two Lockerbie suspects are not handed over.

The pair are accused of conspiring to place a bomb concealed in a radio cassette recorder in a suitcase on board an Air Malta flight that connected to Pan Am 103 in Frankfurt.

The bomb exploded over Lockerbie on 21 December, 1988, killing all 259 people on board and 11 on the ground.

Police in Scotland and the US originally suspected the Syrian-based Popular Front for the Liberation of Palestine - General Command (PFLP-GC) of having a role in the bombing.

But further evidence led the authorities to conclude that Libya ordered and carried out the attack in retaliation for the downing of an Iranian airliner by a US missile in 1988.

The resolution marks the first occasion the Security Council has told a country to extradite any of its citizens.

It is also the first time the UN has implicitly accused a fellow member state of being involved in state terrorism.

Despite the move, families of the victims of the Lockerbie bombing criticised the United Nations resolution for being weak and inadequate.

"There is ample evidence that both Syria and Iran were involved," said Daniel Cohen whose 20-year-old daughter, Theodora, died in the crash.

"But, because of political reasons the United States and Great Britain have drawn the Pan Am 103 case very narrowly, accusing only two Libyans."

A senior Libyan official said that Tripoli had no intention of extraditing the men.

Jadualah Azuz Talhi, a former foreign minister who led a Libyan delegation, told the security council that the suspects were innocent until proven guilty.

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