Seven schoolgirls and a school official were killed when a freight train struck a school bus in Argentina's western province of San Luis, authorities said.

The bus was carrying 40 people, most of them girls from a private Catholic school who were on their way to a religious event, provincial education minister Marcelo Sosa said.

"The train dragged the bus more than 300 meters (yards)," he added. "There are many injured, some of whom could have to undergo amputation."

Six schoolgirls and a school employee died at the scene of the crash, and another student later died in an intensive care unit at a local hospital, a provincial official told AFP.