A murder investigation is under way after a 20-year-old man was shot dead in Dublin in the early hours of Monday morning.

The incident happened at around 12.15am on the Knocknarea Road in the Drimnagh area.

Several shots were fired from a number of different weapons during the incident, a number of cars and people were involved and one car seems to have crashed into another in what appears to have been a deliberate and planned attack.

Gardaí say an AR 15 assault rifle was recovered from a hedge near the scene of the attack.

The semi-automatic rifle, which can fire hundreds of rounds per minute, is being examined to establish whether or not it was the murder weapon.

Three men were arrested shortly after the shooting. They are being held in garda stations in Dublin and can be questioned for up to three days.

Detectives believe the murder is connected to serious and organised crime but are trying to establish what happened and why.

A suspected pipe bomb was also found near the victim's body and the Army Bomb Disposal Team was called in to make the area safe.

The scene of the shooting has been preserved
Gardaí have cordoned off the scene in Drimnagh

The man's body has been removed from the scene and a post-mortem examination is to be carried out.

Gardaí are appealing for any video footage from the Knocknarea Road area between 11.30pm and 12.30pm last night.

They are also looking for any CCTV footage in the wider area of Cooley Road, Brandon Road, Errigal Gardens, Crumlin Road, Slievenamon Road, Mourne Road and associated side roads.

Anyone with information is asked to contact Sundrive Road Garda Station on 01-666-6600, the Garda Confidential Line on 1800 666 111 or any garda station.

Attack in Drimnagh 'completely unacceptable' - McEntee

"The attack in Drimnagh last night was completely unacceptable and is not something we will tolerate on our streets," said Minister for Justice Helen McEntee.

"I commend the gardaí for responding quickly, resulting in the speedy arrest of suspects. Tackling crime and ensuring safer streets continues to be a top priority for An Garda Síochána and the Government," she added.

Pascal Connor, a resident in Drimnagh heard a "commotion" near his home just after midnight.

"As far as I know there was three cars down here involved in what I thought was an accident. Someone said there was a shooting."

"I spoke to other neighbours and they said there was shots fired.

"Around their area it's very quiet, it’s hard to take when you live around the area. You don’t expect it on your doorstep," added Mr Connor.

Additional reporting Dimitri O'Donnell