The family of a man with special needs has condemned an attack on him at a public park in Dublin, which left him needing stitches for a large wound to his head.

During the attack, believed to have involved three teenagers, Paul Deaton, 31, was told he would be set on fire and the youths laughed when he fell hurting his head after they tripped him.

"Paul is traumatised by what happened," said his sister Linda Deaton, who stayed with him in Beaumont Hospital where he had four staples inserted to close his head wound.

The attack has also been condemned by Dublin's Lord Mayor Christy Burke.

"I sincerely hope this is an isolated incident," he said. "Are we getting to the stage where we need to put in park rangers to patrol the park?"

Ms Deaton said her brother "is really gentle and wouldn't say boo to anyone".

He lives at home in Marino with his older brother Brian and their mother Dorothy.

The family said Mr Deaton left his home to go to Fairview Park and to look at JCBs, which are being used for work near the park.

"Paul loves tractors and diggers and he was taking pictures of them on his phone," Ms Deaton explained.

He went to the park at around 7pm, where he was approached by three youths, who began to harass him.

They tried to hit him and bully him and he tried to get away a number of times.

Ms Deaton said: "He was kicked and eventually he got away, but not before one of them tripped him to stop him. They laughed at him and took out their phones to take pictures of him."

After the attack, Mr Deaton was covered in blood and a stranger came to his aid and brought him to a nearby pharmacy.

"We want to thank the young woman who came to help him. We don't know who she is but we are grateful," she said.

Ms Deaton went to the hospital with her brother, where he had his head stapled and other injuries treated.

The family are hoping that the culprits will be brought to justice and they have reported the attack to gardaí in Clontarf.

They also think the gang may have recorded the attack on their phones.

Ms Deaton said they know one of them had a bicycle. One was wearing a grey top, the second had a black jumper and the third was possibly in a red jumper.

They want anyone who saw anything or can help to come forward.

Mr Burke offered his sympathies and support to Mr Deaton and his family.

"This is an act that is deplorable, despicable and cowardly. I hope it is not a trend. I hope anyone with any ounce of information will report it to the gardai," Mr Burke said.

A garda spokesperson confirmed that the gardai in Clontarf are investigating an assault that was reported to them at 7.45pm on Wednesday.