Sydney police monitoring hostages' social media posts

Posts on social media believed to be from hostages at a cafe in Sydney are being monitored by police.

New South Wales Police Deputy Commissioner Catherine Burn said they were examining sites like Twitter and Facebook for vital clues about what is the happening inside the building.

She told reporters: "That is forming part of our tactical response in how to handle this."

The cafe's owners Lindt said about 10 employees and 30 customers are thought to be inside by cafe on Martin Place.