A suspect is in custody after a shooting at Pittsburgh's Tree of Life synagogue, police say.

A police official has also said there are "multiple casualties" — including three officers.

Police spokesman Chris Togneri said police have no more information at this time because they were still trying to clear the building and determine if any more threats exist.

The synagogue is located at the intersection of Wilkins and Shady avenues. The tree-lined residential neighbourhood of Squirrel Hill, about 10 minutes from downtown Pittsburgh, is the hub of Pittsburgh's Jewish community.