Armed Police Surround Besieged Sydney Cafe

The transcript discusses a developing situation in Sydney, where police have expanded their cordon around Martin Place due to a potential hostage situation at the Lindt cafe. Up to 40 people may be inside, though this is unconfirmed. A flag resembling the Islamic State flag was seen, but it is actually the Shahada flag. The Australian Stock Exchange and other businesses in the CBD have been evacuated. Security is heightened, and traffic is still flowing on nearby streets. The situation is reminiscent of past terror threats in the area.

What is the estimated number of people believed to be inside the cafe during the incident?

What flag was reportedly held up by two people in the cafe?

What developments occurred at the Australian Stock Exchange during the incident?

What actions were taken by the police regarding the area around Martin Place?

What previous security concerns were mentioned regarding Martin Place?