A police officer in Philadelphia was ambushed by a man who pledged allegiance to the so-called Islamic State (IS), officials have said.

Edward Archer fired at least 11 shots at the officer, in an act done "in the name of Islam", police said.

Despite being shot, Officer Jessie Harnett left his vehicle and was able to to return fire, striking Mr Archer at least once.

Jon Sopel reports.