The siege of a local cafe at Sydney's Martin Place, which left two hostages and a gunman dead after an hours-long standoff, has triggered a city-wide, high-visibility operation, New South Wales police announced Tuesday.

“Operation Hammerhead will focus on metropolitan Sydney and primarily involve general duties police. If need be, those officers will be used wherever our operational intelligence dictates,” Assistant Commissioner Mick Fuller said in a statement. “General duties police, as well as specialist commands, will be deployed from the Police Operation Centre which will remain open 24/7 during the operation," he said, adding that locations such as the Sydney Harbor, sporting arenas and other public venues would also be monitored.

The operation, which is scheduled to commence Tuesday night, will be conducted 24 hours a day over the next three weeks. Fuller also urged the people of Sydney to continue with their “day to day business with confidence and comfort in the knowledge they are safe.”

Meanwhile, Australian Prime Minister Tony Abbott paid tribute to the two hostages who died in the standoff at the Lindt Chocolat Café on Monday, by offering flowers at a makeshift memorial in Sydney on Tuesday. Abbott and his wife, Margaret, also signed condolence notebooks set up at the site.

Several mourners also reportedly placed flowers and cards on the fence adjoining the building where the siege, which lasted for 16 hours, took place. Abbott reportedly appeared at a news conference after visiting the memorial, and said that authorities would investigate why Man Haron Monis, the gunman who held 17 people hostage, was out on bail despite serious charges against him in separate cases.

"How can someone who has had such a long and checkered history not be on the appropriate watch list? And how can someone like that be entirely at large in the community?" Abbott reportedly said. "These are questions we need to look at carefully and calmly and methodically. That's what we'll be doing in the days and weeks ahead."

Australia's Grand Mufti, Professor Ibrahim Abu Mohammed, was also among those who laid flowers at the makeshift shrine.

“Today we are here, all of us, Australians grieving our great loss,” Sheikh Aref Chaker, a spokesperson for the Mufti reportedly said. “We will be standing united and strong with our fellow citizens and we will not allow anyone to rob us of our values of tolerance and peace.”