One of the suspected perpetrators, identified as an Islamic State group sympathiser, was shot dead by police following Tuesday night's shootings in the Austrian capital that have left four people dead.
A manhunt is currently underway for an assailant still at large. Police in Austria are liaising with federal officers in Germany.
Tightened controls at the border between Germany and Austria is now a “tactical priority” for the federal police force, a spokesman for German federal police told news agency AFP.
German Chancellor Angela Merkel condemned the shootings, saying: “Islamist terror is our common enemy”.
“The fight against these assassins and those who instigate them is our common struggle,” Merkel's spokesperson said, adding: “solidarity” with Austria.
The first shots were fired shortly after 8pm near the Schwedenplatz underground station in Vienna. After that shots were fired at five further locations in the city.
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Merkel expressed her shock at the suspected terrorist attack. “In these terrible hours when Vienna has become the target of terrorist violence, my thoughts are with the people there and the security forces who are facing danger,” the Chancellor said in her statement.
“We Germans stand in sympathy and solidarity with our Austrian friends,” she added.