Eyewitnesses have spoken of "a kind of bomb" that exploded at the entrance of the gurudwara around 7 pm local time yesterday where a wedding had taken place.
About 200 people, including many children, were present at the wedding that began very late and was ongoing when the explosion occurred, the Bild newspaper reported quoting an eyewitness.
Reacting to the incident, External Affairs Ministry spokesperson Vikas Swarup said the Indian mission here is following it up with German authorities.
A 60-year-old suffered serious injuries and had to be hospitalised while two 47- and 56-year-old men had minor injuries, the report said but did not specify if all of them were Sikhs.
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The injured included a priest on whom the whole pane of glass had fallen due to the impact.
A police spokesman said that the explosion was probably caused deliberately.
A masked man wearing dark clothes fled in an SUV, according to several witnesses from the scene.
Three men were arrested following the explosion over suspicion that they were in the black SUV, which had previously been seen in the vicinity of the crime scene.