Malala Yousafzai finishes school and joins Twitter

Teenage Nobel Peace Prize winner Malala Yousafzai has left school after completing her A-levels - announcing the event in her first tweet.The young activist said her achievement was "bittersweet" given that millions of girls around the world may never get to complete their education.Malala was shot in the head by a Taliban gunman in 2012 for campaigning for girls' education in her native Pakistan.