Five people have fled from a cafe in the heart of Sydney where a dramatic hostage taking is unfolding Monday . But an unknown number of people remain in the cafe , held by at least one armed hostage taker . Hundreds of police officers have shut down a usually bustling area in Australia 's most populous city amid the crisis . Chilling images from local media showed people , believed to be hostages , with their hands pressed against the glass of the Lindt Chocolate Cafe in Sydney 's central business district . Footage showed them holding up a black flag with Arabic writing on it that reads : `` There is no God but God and Mohammed is the prophet of God . '' Three people who were seen running out of the cafe `` are now out of the building and they are now with police , '' said New South Wales Police Deputy Commissioner Catherine Burn , declining to give details about whether they escaped or were let go . Video from CNN affiliate Seven Network later showed two more people running out of the cafe . Authorities said many of the details about the situation remained unclear , including the number of people inside the cafe and the motivations of the hostage taker . `` We do n't know whether this is politically motivated , although obviously there are some indications that it could be , '' Australian Prime Minister Tony Abbott told reporters . The Islamic writing on the banner stoked fears that the crisis in Sydney could be linked to extremists . Australia , which is part of the international coalition fighting the terrorist group ISIS in the Middle East , said in September that it had foiled a plot by Islamic militants to carry out a public execution . New South Wales Police Commissioner Andrew Scipione said it was n't yet clear whether the situation at the cafe was a terrorist event but that police are on `` a footing that would be consistent with a terrorist alert . '' Burn said police negotiators are now in contact with a hostage taker , who appears to have taken staff and customers captive as people were heading to work on Monday morning in the Martin Place area . Chris Kenny , an editor at The Australian newspaper , said he was at the cafe Monday morning . He left shortly before the siege started . `` As police quickly swarmed and cleared the area , I turned to see a man against the window , facing out with his hands raised , '' he wrote in his account of the incident . `` At first I was relieved thinking this was the gunman responding to police -- but soon the awful realisation the customers were being forced against the windows . '' Seven Network reported that at least 13 people are being held at the cafe , but Scipione declined to say how many were in there . Police barricaded off streets and evacuated buildings near the cafe , bringing an eerie quiet to a district typically buzzing with pedestrians and vehicles . The Martin Place train station was shut down , according to police . They urged people to stay away from the area , but some local office workers gathered at the scene to try to find out what was going on . The buildings evacuated included the U.S. Consulate General , said Alicia Edwards , a spokeswoman . All personnel have been accounted for , although it 's not known whether there are any U.S. citizens among the hostages . U.S. President Barack Obama has been briefed on the situation .
At least 50 people have fled the cafe , Seven Network video shows . Police negotiators are in contact with a hostage taker , the report says . Australia 's government says it 's unclear whether the attack is politically motivated . Local media carry images of police holding a black box with Arabic writing .