Earlier, the lone gunman had issued demands and claimed to have bombs scattered around the city, multiple media outlets reported.
The gunman had released videos, through some hostages, stating that he wanted an Islamic State flag and a phone call from Australian prime minister Tony Abbott. He also made bomb threats, media outlets including Sky News Australia were reporting.
Hundreds of heavily armed police officers, many in sniper positions, had taken control of the streets around the Lindt Chocolate Cafe in Martin Place, the heart of the city's financial and shopping district.
Five hostages were able to flee to safety in the first several hours of the standoff. An undisclosed number of hostages remained in the cafe until the fiery resolution, police said.
Sky News and other media outlets, citing police, identified the suspect as Man Haron Monis, 49, an Iranian-born, self-proclaimed spiritual healer with a lengthy criminal record who is currently free on bail.
"We are doing all we can to set you free," New South Wales state police Commissioner Andrew Scipione had said at a press conference hours after the crisis began. The incident began at around 9:45 a.m Monday local time. Sydney is 16 hours ahead of New York.
Three people ran out of the cafe six hours into the hostage crisis. About an hour later, two women wearing aprons with the Lindt chocolate logo fled the cafe into the arms of heavily armed police officers.
Kathryn Chee, who works at the cafe, told ABC News she had planned to arrive at work early when her mother told her the news of the incident.
She said she saw pictures on TV of hostages with their hands against the windows.
"Straight away, there were three people that I knew....my heart just sank," she said. 'It's just a little cafe, we have regular customers, people we know their orders…we're already making their order before they get to the counter."
Australian Prime Minister Tony Abbott urged Australians to go about their business as usual in a speech from Canberra on Monday.
"Our thoughts and prayers must above all go out to the individuals who are caught up in this," he said.
He earlier said the events may be "politically motivated.''
New South Wales Police Deputy Commissioner Catherine Burn earlier said negotiators talked with the gunman for several hours.
The Sydney Morning Herald reported that the gunman forced hostages to call multiple media outlets to outline his demands, and that the hostages also posted his demands on their social media accounts.
Police had asked that media outlets do not report the gunman's demands, but the information circulated quickly.
The standoff gripped downtown Sydney, shutting down government offices, public transit and schools as it dragged through the day. The normally busy and crowded business district of the city was on virtual lockdown.
Seven Network television news staff watched the gunman and hostages for hours from a fourth floor window of their Sydney offices, opposite the cafe.
The gunman could be seen pacing back and forth past the cafe's four windows. Reporter Chris Reason said he carried what appeared to be a pump-action shotgun, was unshaven and wore a white shirt and a black cap.
Network staff counted about 15 different faces among hostages forced up against the windows.
Australia raised its terror warning level in September in response to a domestic threat posed by supporters of the Islamic State group. At the time, one man arrested during a series of raids in Sydney was charged with conspiring with an Islamic State leader in Syria to behead a random person in downtown Sydney.
Meanwhile in Belgium on Monday, police detained three men after reports of a hostage taking in an apartment building in the western city of Ghent. No one was injured in the incident.
Federal police spokeswoman Annemie Serlippens excluded any political or terror motive. Police, who blocked off a wide perimeter around the area, said it was still unclear whether they had taken any hostages.
source: usatoday.com by William M. Welch, Jane Onyanga-Omara and John Bacon,