A man has fallen to his death while being winched to safety during a rescue operation in bushland northeast of Melbourne.

An air ambulance was sent after the man injured his leg while bushwalking near Mansfield at about 12.30pm (AEST) on Saturday.

The man fell as he was being winched to safety.

Ambulance Victoria CEO Greg Sassella said in a statement that Ambulance Victoria had immediately suspended winching operations and would assist all investigating authorities.

"Our thoughts and sympathies are with the man's family. We are also providing support to the flight crew and paramedics involved," Mr Sassella said.