Memorial services are to be held in Scotland and the US to remember the 270 people killed when a passenger plane exploded over Lockerbie 30 years ago.

Wreaths will be laid in the Dumfries and Galloway town where the wreckage of the bombed Pan Am Flight 103 came down on the night of December 21, 1988.

Eleven people died in Lockerbie, along with the 259 passengers and crew on board the New York-bound plane which had set off from Heathrow.

Scottish Secretary David Mundell, who is from the town, will attend a service at Dryfesdale Cemetery where prayers will be said for all those affected by the biggest mass murder on British soil in recent history.

A message of prayer and good wishes from the Queen to those marking the "solemn anniversary" will be read by Lord Lieutenant for Dumfriesshire, Fiona Armstrong.

Mr Mundell said it had taken only a few seconds for Lockerbie to go from a small, quiet town to the centre of global attention.

Speaking ahead of the service, the MP for Dumfriesshire, Clydesdale and Tweeddale said: "It has not been easy, nor have we been able to achieve the closure we would have wanted, even after 30 years.

"However, throughout, the people in Lockerbie have retained their dignity and stoicism, and offered friendship and support to those who lost loved ones.

"The relationship that has developed between Lockerbie Academy and Syracuse University is one of the few positives to come from that night, along with all the other personal relationships that have been forged.

"Strengthening and deepening those relationships must be our priority as we look to the future."

A memorial mass will also be held later at the town's Holy Trinity RC Church. Canon Patrick Keegans, who was parish priest in Lockerbie in 1988, will speak of the aftermath of the disaster in his homily.

The majority of those on board the jet were American citizens, including 35 students of Syracuse University in New York State.

A memorial will be held at the university, and around 500 people are expected to gather at Arlington National Cemetery in Virginia where a cairn made from Lockerbie stone stands in memory of those who died.

Solicitor General for Scotland Alison Di Rollo will attend the service along with a representative from Police Scotland.

Pam Am Flight 103 was blown up by the detonation of an explosive stored in a suitcase in the plane hold. Many believe the atrocity was committed in revenge for the downing of an Iran Air passenger flight by a US missile cruiser earlier in 1988.

The only person ever convicted of the bombing, former Libyan intelligence officer Abdelbaset al-Megrahi, died in 2012 after being released from Greenock jail on compassionate grounds.

His family and some relatives of the Lockerbie victims believe he was the victim of a miscarriage of justice and are fighting to clear his name.

The Scottish Criminal Cases Review Commission is currently determining whether a fresh appeal against the conviction should proceed to the courts. Aamer Anwar, lawyer for Megrahi's family, said: "The reputation of the Scottish law has suffered both at home and internationally because of widespread doubts about the conviction.

"The only place to determine whether a miscarriage of justice did occur is in the Court of Appeal, where the evidence can be subjected to rigorous scrutiny. We hope that can finally take place next year."

Three decades on, the investigation into the bombing itself continues, with prosecutors pledging to track down Megrahi's accomplices.

A Crown Office spokeswoman said: "Prosecutors and police, working with UK Government and US colleagues, will continue to pursue this investigation, with the sole aim of bringing those who acted along with Al Megrahi to justice."