At least one gunman has opened fire at a Sikh temple in the midwestern U.S. state of Wisconsin.

Police say the shooting occurred Sunday morning at around 10:25 a.m. local time at the Sikh Temple of Wisconsin, located outside of Milwaukee.

A police spokesman said an officer responding to the shooting engaged a suspected gunman with both sustaining injuries.

The spokesman says tactical officers are attending to an unknown number of victims inside the temple.

It is unclear whether another gunman remains inside the building.