A large police operation is under way at a Vienna synagogue following gunfire, officers in the Austrian capital said.

“There are several injured persons,” police tweeted. “We are on site with all available forces. Please avoid all public squares in the city.”

Austrian public broadcaster ORF cited witnesses as saying that several shots were fired shortly after 8pm local time. The police operation is taking place in the centre of Vienna, close to the Danube river.

Vienna police also tweeted that the exact circumstances of the incident were still being determined.