A "thorough, impartial and objective" investigation into the death of Sheku Bayoh in police custody will be delivered, the Lord Advocate has pledged.

Frank Mulholland told MSPs that the family of Mr Bayoh, 31, who died after being restrained by officers in Kirkcaldy, Fife, on May 3, have been given assurances the investigation will be completed as soon as possible.

He also confirmed that a fatal accident inquiry into the death will be held, regardless of any criminal proceedings.

Mr Muholland was asked to update Holyrood on the investigation into Mr Bayoh's death following the submission of an interim report by the Police Investigations and Review Commissioner (Pirc) last month.

Mr Bayoh's family have complained there are "too many questions and not enough answers, no transparency".

The Lord Advocate said further work by Pirc was needed, particularly into the cause of death, before their investigation is completed.

"Regardless of the outcome of the investigation, who can fail to sympathise with the family for their loss?" Mr Mulholland said.

"Having met the family on two occasions, I know the effect that this tragedy has had on them and they have borne their loss with great dignity.

"They are right to demand answers and a thorough, impartial and objective investigation is what they deserve."

Mr Mulholland said he was confident this could be done "expeditiously without compromising thoroughness".

He added: "Regardless of the decision on criminal proceedings, there will be a fatal accident inquiry.

"A fatal accident inquiry is mandatory, Sheku Bayoh's death being a death in custody.

"A fatal accident inquiry will allow all the evidence to be presented in a court, open to the public and the media, to be rigorously tested by all parties represented at the FAI, including the family, and allow the sheriff to make findings in fact and recommendations in relation to Sheku's death in a judgement that will be available to all."

Aamer Anwar, solicitor for Mr Bayoh's family, said: "The Bayoh family welcome the comments of the Lord Advocate today and his determination to deliver a robust and impartial inquiry into the death of Sheku Bayoh.

"The family have always known that there would be an FAI but they do not believe at this stage that this is a solution to the death in custody of Sheku Bayoh.

"An FAI is, in essence, the bare minimum of what can happen, but at this stage it would be premature to predict the outcome of the investigations if they are truly robust and impartial.

"It has been 19 weeks since Sheku's death and the family hope the Lord Advocate can provide them with the truth of what happened, because without that they know there can be no justice."