Police search social media for hints on siege motive

Police are scouring social media, including Twitter and Facebook, to get a better idea of what is happening inside the Sydney siege.

At least one hostage appears to have posted on Facebook about Monday's siege and some of the gunman's demands.

The post has since been taken down.

Scores of police officers are monitoring social media channels for posts like these that help shape how they handle the tense stand-off.

"We are monitoring what is happening (on Twitter and Facebook) and that is forming a part of our tactical response in how to handle this," NSW Deputy Commissioner Catherine Burn said.

Ms Burn said a number of mediums were being used but the community needed to be careful not to overreact.

"We are aware of that and we are monitoring it and we are using it as part of our strategy," she said.