A suspected Islamist gunman was holding hostages inside a chocolate shop in Sydney on Monday and appeared to be making demands to negotiators through Facebook and local media.
Five hostages managed to flee the building, but police would not confirm how many were still being held inside the Lindt cafe — where a black flag used by Islamist groups in the Middle East has been shown in the window.
Australia's Prime Minister Tony Abbott said the gunman was "claiming political motivation" but after almost 13 hours had yet to declare the siege a terrorist event. However, police said they were "operating according to our counter-terrorism protocols."
Chris Reason, a journalist with NBC News' Australian partner Channel 7, said the hostage-taker was "forcing them to stand against windows, sometimes two hours at a time." He added that the suspect seemed to be "getting extremely agitated" after the five hostages left.
Radio station 2GB and television channel 10 News said they each been contacted by hostages to pass on the gunman's demands. An Australia Broadcasting Corporation reporter said she knew the identity of the suspect but would not reveal it at the request of police.
As the lights inside the cafe were switched off late Monday, police said posts on Facebook and Twitter were being investigated but did not say if they had established direct contact with the gunman.
"We are monitoring all forms of communication — Facebook, Twitter — for any information that might assist," said Catherine Burn, deputy police commissioner in New South Wales state. "We're monitoring what is happening on Facebook … that is forming part of our tactical response."
As the standoff entered its 13th hour, New South Wales Police Commissioner Andrew Scipione said nobody appeared to have been injured.
"We have the very best negotiators in the world on the job right now," he told reporters. "Our plan, our only goal tonight is to get those people that are currently caught in that building out of there safely. For those that may be in that building rest assured we are doing all we can to set you free."
Asked about reports that hostages were being forced to use social media to pass on the gunman's demands, Scipione said: "There's no place on earth that doesn't have access to social media. Our plans are built around that."
He said police were in "contact" with the hostage-taker but added "the means by which we're communicating is something we'd rather keep close to our chest."
Scipione said reports of bomb threats in other parts of Sydney had been investigated but there not did not appear to be a danger. "We are only at this stage dealing with one location we are not concerned at this stage about any other," he added.
The drama began shortly after 9:45 a.m. local time (5:45 p.m. ET Sunday). Lindt Australia Chief Executive Steve Loane told Sky Business there were "probably 30 customers" in the cafe and 10 workers. Police refused to confirm the numbers involved.
The first hostages to emerge were three men, who ran out of side exits toward armed police six hours into the siege. An hour or so later, two women ran out. Authorities wouldn't say whether the hostages had escaped or were freed by the gunman, but they dashed out of the cafe in panic.
Nearby streets and office buildings were evacuated and police were seen using ladders to rescue bystanders — including babies — from the building's other floors. The U.S. Consulate in Sydney was evacuated and all U.S. personnel had been accounted for, the State Department told NBC News.
The Lindt Chocolate Cafe is in Martin Place, a busy tourist, transportation and shopping district home to several major banks — including the Reserve Bank of Australia — as well as the state Parliament. The nearby Sydney Opera House cancelled Monday night's performances.
The flag shown in the cafe's window as the hostage drama unfolded appeared to be the Tawhid Banner. NBC News terrorism analyst Evan Kohlmann, added that it was frequently used by Jabhat Al-Nusra and other armed Islamist groups in the region — but not ISIS.
Grand Mufti Ibrahim Abu Mohamed, the highest Islamic office holder in Australia, said in a statement that the Muslim community was "devastated" by the incident, adding that "such actions are denounced in part and in whole in Islam."
The hostage incident comes after police carried out a series of major anti-terrorism raids throughout Sydney in September. ISIS spokesman Abu Muhammad al-Adnani has also urged Muslims in Australia to carry out "lone-wolf" attacks against civilians, according to terrorism analysts at the SITE Intelligence Group.
It was one of the biggest security operations in Sydney a January 1984 when Turkish-born man went on a bank robbery spree, taking 11 people hostage and fleeing the scene before being shot dead in a dramatic road chase. In February 1978, a bomb outside the Sydney Hilton killed to garbage truck workers.
NBC News' Andrea Mitchell, Marc Smith, Matthew Grimson and Jason Cumming and Reuters contributed to this report.
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