VIENNA — A large-scale police operation is ongoing in Vienna following reports of gunfire, police in the Austrian capital said.

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

Initial reports that a synagogue was the target of an attack couldn't immediately be confirmed.

Austrian news agency APA quoted the country's Interior Ministry as saying that one attacker has been killed and another could be on the run.

Police added that the exact circumstances of the incident were still being determined.

Austrian public broadcaster ORF cited witnesses as saying several shots were fired shortly after 8 p.m. (1900 GMT). — Developing