Tony Abbott on Sydney siege: 'A very disturbing incident'

Australian Prime Minister Tony Abbott has said the incident in which people have been taken hostage at a cafe in the centre of Sydney is "very disturbing".

But Mr Abbott also urged Australians to "go about their business as usual".

Pictures on Australian television have shown people with their hands up against a window, and a black flag with Arabic writing.

Hundreds of armed police have sealed off the normally busy Martin Place in Sydney's central business district.