Scotland's most senior law officer has vowed to bring the perpetrators of the Lockerbie bombing to justice.

Lord advocate Frank Mulholland said he would be "failing in his duty" if he failed to find the people who were responsible for the bombing.

He was speaking on the 23rd anniversary of the 1988 atrocity, in which 270 people died when Pan Am Flight 103 exploded in the skies over Lockerbie.

Abdelbaset al-Megrahi remains the only man convicted of the bombing.

Speaking ahead of a US ceremony at Arlington cemetery, Virginia, on Wednesday to commemorate the lives lost, Mulholland said: "I think I would be failing in my duty if I didn't properly seek to take advantage of the opportunity that has opened up with the fall of Gaddafi.

"I am determined to get the answers these families deserve."

Megrahi was released on compassionate grounds from Greenock prison in August 2009, when doctors advised he had around three months to live after he was diagnosed with terminal prostate cancer.

Amin Khalifa Fhimah also stood trial with Megrahi, but was acquitted of any involvement.

Mulholland said the idea that Megrahi had acted alone was "risible", and said "justice has only partly been done".

On Tuesday, he met with the FBI director Robert Mueller III and the US attorney general Eric Holder to discuss the opportunities for stepping up the investigation in Libya into the bombing.

Scotland is preparing to send police officers to Libya to continue with the investigation.

He said: "Opportunities have opened up in Libya this year and we are determined to seek to exploit the opportunities to get to Libya, to get Scottish police officers in there and seek out any evidence that is available.

"Justice has only partly been done. The evidence pointed to it being an act of state-sponsored terrorism.

"Megrahi was a member of the Libyan security service – it is risible to think that he acted alone. What we want to do is bring the others to book.

"A huge opportunity has opened up. It was very difficult when Gaddafi was alive and in power in Libya, and the answers are in Libya."

A representative of the new Libyan government has been invited to attend a memorial service for victims of the Lockerbie bombing in the United States.

Libya's ambassador to the US Ali Aujali is to address relatives of the victims at the remembrance service at Arlington.

It is thought it will be the first time a Libyan politician has attended an event to commemorate Lockerbie.

Mulholland said: "Libyan government ministers have been making statements that are very welcome.

"It is very symbolic that the new Libyan ambassador is attending today. I think that is a huge symbolic statement and it is very welcome and I look forward to what he has to say."

The lord advocate was due to lay a wreath on behalf of the people of Scotland and make a short speech in remembrance of the victims of the atrocity. He was then due to meet the US relatives of the victims.