A man has been arrested in connection with the disappearance of six-year-old Mary Boyle in Co Donegal more than 37 years ago.

Mary went missing from her grandparents' home in Cashelard, Ballyshannon on 18 March, 1977.

She had been playing outside when she followed her uncle across the fields near the house. She turned back but has not been seen since.

A 64-year-old man was detained by detectives from the northern region following a three-year case review.

He is a convicted sex offender who is currently serving a sentence at Midlands Prison in Portlaoise.

He is being held at Mullingar Garda Station on suspicion of kidnapping and can be questioned for up to 24 hours.

Gardaí said the case has always remained a live investigation.

They have carried out searches, issued new appeals and reviewed the case a number of times since Mary's disappearance.

They have also received help from forensic and geology experts.

Assistant Commissioner Northern Region Kieran Kenny said: "We are appealing for anyone with any information on the circumstances around Mary's disappearance to contact us.

"Even something that people may have thought was insignificant at the time could help us advance the continuing investigation."

Mr Kenny said new evidence led to today's arrest and that Mary Boyle's mother is being kept informed of the latest developments.

He said a dedicated team were working on the investigation and today's development is a direct result of new evidence which emerged following the most recent review of the case which began in 2011.

Mr Kenny said that he would like to think that today's arrest could bring the case closer to a resolution but it was too early to say at this stage.

The suspect was arrested at midday under a Section 42 warrant which allows gardaí to arrest people in prison.

Gardaí have asked anyone with information to contact Ballyshannon station on 071-9858530 or the confidential line on 1800-666-111.

Mary Boyle's twin sister Anne Doherty said she was shocked when she heard of the news of the arrest, saying that the family had no prior information about the arrest and were in deep shock.