Two people have been killed and another two seriously injured after a masked gunman tried to break into a synagogue in the east German city of Halle.
In a statement, German interior minister Horst Seehofer said: "Based on current information, we have to assume that it was at least an antisemitic attack.
"According to the federal prosecutors' office, there are enough indications that it was possibly a right-wing extremist motive. They have taken over the investigations."
Police have arrested one suspect, who according to Der Spiegel is a 27-year-old man from the state of Saxony-Anhalt.
Footage from the attacks was livestreamed on Amazon's video gaming platform Twitch.
Max Privorozki, Halle's Jewish community chairman, described how the gunman tried to shoot his way into the synagogue where up to 80 worshippers were marking Yom Kippur, the holiest day of the Jewish calendar.
"We saw via the camera system at our synagogue that a heavily armed perpetrator with a steel helmet and a gun tried to shoot open our doors," he told the Stuttgarter Zeitung newspaper.
"The man looked like he was from the special forces... But our doors held.
"We barricaded the doors from inside and waited for the police."
One woman was shot dead outside the synagogue, while a man was killed inside a nearby kebab shop.
Conrad Roesler was in the restaurant when the attack happened. He told n-tv television: "He had an assault rifle and a helmet and suddenly he threw what looked like a grenade.
"It bounced off a door frame... Suddenly he picked up the rifle and fired at the shop... I hid in the toilet."
Earlier reports had suggested there were multiple attackers, with police warning residents to stay at home, and the city's train station was closed.
Several hours later, they announced there was no longer an "acute" danger to the population and residents could go back into the streets.
News agency dpa and newspaper Bild cited unidentified security sources as saying the evidence points to a lone assailant.
German foreign minister Heiko Mass wrote on Twitter: "That on the Day of Atonement a synagogue was shot at hits us in the heart.
"We must all act against antisemitism in our country."
In Berlin, the state interior senator urged police to step up security at Jewish institutions in the German capital.
A spokesman for Twitch said: "Twitch has a zero-tolerance policy against hateful conduct, and any act of violence is taken extremely seriously.
"We worked with urgency to remove this content and will permanently suspend any accounts found to be posting or reposting content of this abhorrent act."