PM Abbott: 'We have to ask if could have been prevented'

An investigation has been launched into the police operation which ended a siege in a cafe in Sydney, Australia.

Two people died, along with the gunman, as police commandos stormed the cafe in Martin Place in the heart of Sydney early on Tuesday morning.

Australia's prime minister Tony Abbott said questions would be asked about whether the attack could have been prevented and why the gunman, Man Haron Monis, was not on a terror watch list.