Two young Swiss men were arrested near Zurich on Tuesday in connection with the deadly shooting rampage in Vienna, Swiss police said.

“Police investigations led to the identification of an 18-year-old and a 24-year-old Swiss citizen,” Zurich police said in a statement, adding that the two men had been arrested Tuesday afternoon in Winterthur “in coordination with the Austrian authorities.”

“The extent to which there is a connection between the two people arrested and the alleged assassin is currently the subject of investigation,” the statement said.

Four people were killed during the assault in Vienna on Monday night that saw Kujtim Fejzulai, a 20-year-old described as an Islamic State group sympathiser, open fire with an automatic weapon in a busy area of the historic Austrian capital before being shot dead by police.

Austrian police said Tuesday that Fejzulai was a know Islamic extremist who had spent time in prison.

Swiss authorities, including Zurich police, had said earlier Tuesday that they were investigating any possible links between the Vienna attack and Switzerland.

Zurich police said they had created a special working group to probe any specific links with the northern Swiss canton.,Upon announcing the two arrests, Zurich police said they were working closely with national Swiss police and the Austrian police.

“Complete clarification of any possible involvement (of the suspects) is the highest goal of both countries’ security services,” it said.