A 14-year-old boy has been killed and five people seriously wounded in a knife attack in southern Austria.

Police said the suspect is a 23-year-old Syrian asylum seeker who was detained at the scene in Villach, a town near the Italy and Slovenia border.

Police are yet to establish a motive but have involved extremism specialists in the investigation, a spokesman told the BBC.

The incident took place around 16:00 local time (15:00 GMT) near the town’s main square. Two of the five people injured were in a serious condition as of Saturday evening.

A delivery worker who had driven his vehicle at the attacker helped prevent more injuries, police said.

The driver – also a Syrian man – said he witnessed the attack as he was driving by and deliberately rammed the knifeman.

The suspect was arrested shortly after by two female police officers. As of Saturday evening, he was still being interrogated, police said.

Some witness reports initially indicated a potential second attacker, leading to police shutting down train travel in the attack’s immediate aftermath.

However, local police told the BBC they were confident only one knifeman was involved.

Austrian law means the attacker’s identity has not been released but police confirmed he is a 23-year-old Syrian man who lived locally.

He had a temporary residence permit and was waiting for a decision on his asylum application.

Police initially said four people were wounded but a fifth person later came forward with minor injuries.

The identity of the teenager who was killed has also not yet been disclosed.

Governor Peter Kaiser of Carinthia, the region where Villach is located, described the attack as an “unimaginable atrocity”.