Sydney – On Monday Australian police said ┬ánegotiators had been in contact with the gunman holding hostages in a Sydney cafe siege but refused to speculate on his possible motivation.

Six hours after the mid-morning siege began, television showed three hostages running out of the Lindt chocolate cafe and sheltering behind a heavily armed, black-clad SWAT team.

Police said it was not known exactly how many more hostages remained in the cafe but it was not as high as the 30-40 that had been reported earlier. The remaining hostages were being held by at least one armed assailant, police said, but did not rule out that others could be involved.

Prime Minister Tony Abbott, who has warned of militant plans to strike Australian targets, said there were indications the hostage situation at the cafe was politically motivated.

“This is a very disturbing incident. I can understand the concerns and anxieties of the Australian people,” Abbott told reporters in Canberra, without providing any information on the siege.

Australia, a staunch ally of the United States and its escalating action against the Islamic State in Syria and Iraq, is on high alert for attacks by home-grown militants returning from fighting in the Middle East.

“We have moved to a footing that would be consistent with a terrorist event,” Andrew Scipione, police commissioner for the state of New South Wales, told reporters in Sydney.

The cafe was directly opposite a commercial television studio and footage earlier showed several people inside the cafe standing with their hands pressed against the windows.

Pictures showed a black and white flag similar to those used by Islamic State militants in Iraq and Syria being held up by what appeared to be a staff member and another woman. Local media reports said the flag was the Shahada, a general expression of faith in Islam, a translation of which is: “There is no god but Allah; Muhammad is the Messenger of Allah.”

The incident forced the evacuation of nearby buildings in Sydney’s central business district and sent shockwaves around a country where many people have started to turn their attention to the approaching Christmas festive season following earlier security scares.

In September, Australian anti-terrorism police said they had thwarted an imminent threat to behead a random member of the public and days later, a teenager in Melbourne was shot dead after attacking two anti-terrorism officers with a knife.