Two Swiss men suspected of conspiring in a deadly terror attack in Vienna last year have been denied bail, according to media reports.

The duo were aged 18 and 24 when they were arrested in the Swiss city of Winterthur in November, the day after a gunman shot four people dead in the Austrian capital. They were denied bail by a Swiss court on February 5, several newspapers reported on Saturday.

The Office of the Attorney General (OAG) is investigating links between the two suspects and the Vienna gunman, who was shot dead by police during the attack last year. They visited the gunman in Vienna in July and were in social media contact near to the time of the attack, according to the media reports.

Swiss federal prosecutors are also investigating the duo’s possible complicity in attempts to buy ammunition in Slovakia.

Winterthur, located northeast of Zurich, has a recent history of Islamic radicalisation. In recent years, an imam was deported from the city to Somalia for hate preaching and another person, dubbed the “Emir of Winterthur” was sentenced to a 50-month jail term for recruiting jihad fighters. A mosque in the city has also been closed down by the authorities.