A Syrian asylum seeker who went on a vicious knife rampage in Austria was seen "laughing" as he stabbed a 14-year-old boy to death in a suspected Islamist attack.

The 23-year-old man, named locally as Ahmad G., allegedly shouted "Allahu Akbar" before launching into the attack just before 4pm on Saturday afternoon in the southern Austrian city of Villach.

Two men were seriously injured and are being treated at Klagenfurt State Hospital. One suffered eight stab wounds to the back and the other was knifed in his heart.

He stabbed his victims apparently at random as they were walking near the city’s main square and was stopped only after Alaaeddin Alhalabi, also a Syrian, bravely intervened.

The 42-year-old delivery van driver drove into the man in a desperate attempt to stop him. The suspect was then arrested.

"I didn’t think about it, I reacted immediately. I just drove off in the car and hit him" he told the Austrian news outlet 5 Minuten.

Alaaeddin added: "I have lived here with my family for nine years and I love Villach. Villach has given me a lot."

Mayor Günther Albel said: "As mayor, but above all as a father of two children, today’s news from Villach breaks my heart.

"A dead 14-year-old and four others injured – this is the terrible result of a senseless act of bloodshed.

"My sincere condolences go out to the family and friends of the deceased. I wish the injured a speedy recovery.

"And to all those who sow hatred and violence, I say: You will not win."