Canberra, Dec 15 (IANS): An armed man Monday took several people hostage inside a shop in Sydney's central business district, forcing the government to call an emergency security meeting here.

The hostages were seen standing with their hands up at the windows of the Lindt Chocolat Cafe in Martin Place, Sydney. There was also a black and white flag, believed to be a jihadi flag, being held up in a window, Xinhua reported.

Police responded to the siege by blocking off the area, which was crowded with families and children. The local railway station was shut down but flights from the Sydney Airport were unaffected.

"New South Wales (NSW) Police and the Australian Federal Police are currently responding to a reported hostage taking incident in Martin Place in Sydney. I have spoken with NSW Premier Mike Baird and offered him all possible Commonwealth support and assistance," The Sydney Morning Herald quoted Prime Minister Tony Abbott as saying in a statement.

Many buildings in the locality, including the Opera House, New South Wales parliamentary executive offices and the state library, were evacuated.

New South Wales Premier Baird said that he has "full confidence the NSW Police are working effectively" to resolve the situation.

Australian PM calls for calm amid Sydney hostage situation

Australian Prime Minister Tony Abbott called for calm after a gunman took up to 12 hostages in Sydney's city center Monday morning.

"New South Wales (NSW) Police and the Australian Federal Police are currently responding to a reported hostage taking incident in Martin Place in Sydney," Xinhua quoted Abbott as saying.

"I have spoken with NSW Premier Mike Baird and offered him all possible Commonwealth support and assistance."

"The National Security Committee of the Cabinet has also convened for briefings on the situation," said the prime minister.

"This is obviously a deeply concerning incident, but all Australians should be reassured that our law enforcement and security agencies are well trained and equipped and are responding in a thorough and professional manner," he added.

Abbott also confirmed that the federal government would provide further updates as further information becomes available.