All times listed are Singapore time. Refresh this page for updates.

1.17PM: The New Daily reporter Susannah Guthrie (@susguthrie) tweets a photo of hostages escaping from the cafe at Martin Place.

1.03PM: According to NSW Police Force, investigators are still trying to work out the offender's motivations. "We don't believe anyone else in the cafe has been injured,” says Deputy Commissioner Burn.

12.47PM: No reports of Singaporeans affected by Sydney siege, says Ministry of Foreign Affairs Singapore.

“MFA is deeply concerned about this disturbing development and our thoughts are with the hostages and their families. MFA is monitoring the situation closely. We have not received any reports of Singaporeans affected by the hostage situation as of 12pm (Singapore time) on 15 December 2014. The Singapore High Commission in Canberra is contacting Singaporeans in Sydney who have e-registered with MFA and is in touch with the Australian authorities." 

12.46PM: A small number of people - including one wearing a Lindt apron - were seen coming out of a side door adjacent to the Lindt cafe, which was being watched by heavily armed police, reports Free News Australia.

12.43PM: The Grand Mufti of Australia and The Australian National Imams Council have condemned the siege in Sydney as a “criminal act”, saying "such actions are denounced in part and in whole in Islam". (via Reuters)

12.13PM: Sydney Opera House is open to the public again. Tourists were being let back into the world-famous venue by early afternoon, after it was temporarily evacuated following the discovery of a suspicious package in the morning, Reuters reports. 

12.10PM: "We cannot allow these events to shut down our country, to shut down who we are as Australian people," replied Australia's Treasurer Joe Hockey when asked whether the siege in Sydney's retail heartland could deliver a hit to fragile consumer confidence during the pre-Christmas shopping surge, Dow Jones reports.

"We will not be intimidated, no matter how horrific these events can be." 

11.51AM: Lindt Chocolate Cafe Australia releases a statement regarding the siege on its Facebook page.

11.31AM: No impact on flight schedules from Sydney, say low-cost carriers Scoot and Jetstar. In a phone enquiry, Jetstar says it is "still operating as usual" and there is "no impact" on its operation.

"Scoot is closely monitoring the developing situation in Sydney. We are operating flights to and from Sydney as scheduled. We will continue to do so with guidance and advice from the authorities," the spokesperson said.

11.15AM: Uber Sydney says it will offer free rides from the Sydney central business district, after Uber ride prices reportedly hit upwards of A$100 due to a surge of people wanting to leave the area.

10.57AM: New South Wales police hold a media conference. An armed offender is holding an undisclosed number of hostages in the siege; the situation is well-contained and the city will continue to operate, New South Wales police disclose.

There is "at least one" hostage taker, and no direct contact has been made. 

10.50AM: Roads are still closed in Sydney central business district, tweets Live Traffic Sydney.

10.45AM: International leaders send messages of support via social media.

10.20AM: US President Barack Obama has been briefed on the hostage situation, says The White House. 

10.14AM: "We don't yet know the motivation of the perpetrator, we don't know whether this is politically motivated, though obviously there are some indications that it could be," says Australian PM Tony Abbott as he addresses the media in a press conference. "The whole point of politically motivated violence is to scare people out." 

9.50AM: The US Consulate in Sydney has been evacuated. Banks including Goldman Sachs, Bank of America-Merrill Lynch and Nomura have locked their offices in the city centre. 

9.12AM: The US Consulate General Sydney warns American citizens to avoid the area until further notice.

8.15AM: Members of the media monitoring the situation near a cafe in the central business district of Sydney. (Photo: AFP)

7.50AM: As many as 20 people were in the cafe and that there were at least two gunmen, although police had no immediate comment, only confirming than an operation was underway, AFP reports.

7.47AM: Hostages were reportedly held inside a cafe in central Sydney with a siege underway and a flag with Arabic writing held up to a window.