12 people were injured, three of them seriously, in an explosion at a wine bar in the German city of Ansbach on Sunday night, Sky News reports.

Initial reports said the blast was caused by a gas leak, but Bavaria's interior ministry later said the explosion was intentional.

Ansbach Mayor Carda Seidel told the Nord Bayern newspaper that the blast was caused by an explosive device.

The attacker was killed in the explosion. He was reportedly a 27-year-old Syrian who had been denied asylum in Germany.

Bavarian Interior Minister Joachim Herrmann is en route to the area and an operations center has been set up in city hall, according to BNO News.

Germany has been on high alert following a series of incidents in recent days.

The latest such incident occurred earlier on Sunday in the city of Reutlingen in southern Germany, where a 21-year-old Syrian refugee used a machete to kill a woman and injure two others.

German police said the stabber was a "lone operator" and that he "had a dispute" with the woman. They added that as far as the preliminary investigation is concerned, the stabbing did not bear the hallmarks of a terror attack.

That incident followed the shooting in the Olympia shopping mall in Munich on Friday, in which 9 people were murdered, and 35 wounded.

The shooter in that attack has been identified as 18-year-old German-Iranian Ali Sonboly, who reportedly planned the attack for a year.

The series of incidents began last week, when a 17-year-old Afghan refugee attacked train passengers near the city of Wurzberg with an axe and a knife, seriously wounding three people.

The teen, who reportedly shouted “Allahu Akbar” during the attack, was shot dead by police forces as he tried to flee the scene.