DHAKA: At least 40 people have been taken hostage by at least one armed man at a Lindt cafe in the centre of Sydney on Monday.

Lindt Australia executive says there are about 10 staff and up to 30 customers trapped in the cafe.

Hundreds of armed police have sealed off the normally busy Martin Place in Sydney’s central business district, reports BBC.

Pictures on Australian television have shown at least three people with their hands up against a window with a flag of Islamic State (IS), an extremist outfit.

Australian Prime Minister Tony Abbott has described the incident as “deeply concerning”.

He said it was not yet clear who was behind the incident or what their motives were, but said law enforcement agencies were well-equipped to respond.

In a brief news conference, he said the National Security Committee had been briefed, and urged Australians to go about their lives but to be alert.

“I can think of almost nothing more distressing, more terrifying than to be caught up in such a situation and our hearts go out to these people,” he said.

New South Wales Police said in a statement that an “armed incident” was under way, and that “specialist officers are attempting to make contact with those inside a café”.

The police said nearby offices had been evacuated as a precaution and asked people to remain indoors and way from open windows.

Meanwhile, the Grand Mufti and the Australian National Imams Council condemn this criminal act unequivocally and reiterate that such actions are denounced in part and in whole in Islam.

The Grand Mufti, the Australian National Imams Council and the Muslim community express their full support and solidarity with the victims and their families and aspire to a peaceful resolve to this calamity.

Martin Place is a public pedestrian thoroughfare through the heart of Sydney, joining its parliamentary, legal and retail districts.

BDST: 0846 HRS/Updated 1108 HRS, DEC 15, 2014