A mosque in the US state of Minnesota was bombed as people gathered for prayers, the police said. No injuries were reported in the early-morning blast at the Dar Al Farooq mosque in Bloomington on Saturday.

However, the building sustained damage to its front, and photographs from the scene showed a large shattered window, singed blinds and charring around the outside, the New York Times reported.

The Federal Bureau of Investigation (FBI) was investigating the blast and said in a tweet that a homemade explosive device caused the explosion, according to a CNN report.

The Minnesota chapter of the Council on American-Islamic Relations (CAIR) has offered a $10,000 reward in the case. "If a bias motive is proven, this attack would represent another in a long list of hate incidents targeting Islamic institutions nationwide in recent months," said Amir Malik, CAIR's civil rights director in Minnesota.

Law enforcement authorities did not say whether they were investigating the mosque explosion as a hate crime.