Liza Minnelli collapsed on stage during "A Classic Christmas Night"

U.S. singer and actress Liza Minnellicollapsed on stage during a performance in Sweden and was rushed back to the United States for medical treatment, a concert promoter said.

In a separate statement, released by concert organizer Svensk Nojesutveckling, Minnelli's manager Gary Labriola said: "We don't yet know what happened, we are all very worried."

Minnelli was performing alongside several Swedish artists in a show called "A Classic Christmas Night." It was the fourth and final show in a series of four concerts in Sweden, Rosenberg said.