Gardai in Bridewell are investigating the circumstances surrounding the incident in Dublin city centre.
A spokesperson confirmed that the assault occurred during a robbery at North Strand Road at approximately 4.30am.
Two men, aged in their late teens, were walking home when two youths approached them and robbed them. One of the men was seriously injured during the robbery.
Reports suggest he suffered a number of stab wounds to his side as he fled attackers trying to steal his mobile phone.
An ambulance was fortunately passing by the scene shortly after the incident and stopped for the injured man.
He was removed and rushed to the Mater Hospital. His condition is described as serious.
No arrests were made, the spokesperson said, and the scene is preserved. Investigations are ongoing.
Elsewhere in the city, a man in his 20s was critically injured during an attack in Temple Bar last night. The victim was rushed to St James's Hospital where he is believed to be fighting for his life.
Gardai issued an appeal to the public for information regarding the attack, which was said to have been filmed by onlookers.
Three men were arrested at the scene and are being questioned at Pearse Street and Irishtown garda stations.