Police patrols ramped up across Sydney in wake of cafe siege

A high-visibility police operation has started across Sydney following the fatal Martin Place siege with patrols increasing at popular areas.

Beginning on Tuesday evening, officers working under Operation Hammerhead will patrol popular spots, sport venues and other large public events around the clock for the next three weeks.

"Our aim is to provide and maintain high levels of public safety to ensure all NSW residents are safe and ... feel safe," Assistant Commissioner Mick Fuller said.

Police from the transport command, dog squad, riot squad, highway patrol and mounted units as well as those from other branches will be involved.

Road closures enforced around Martin Place since Monday have been eased with Elizabeth Street, Macquarie Street and Hunter Street reopened.

Parts of Martin Place, Phillip Street and King Street will remain closed while authorities investigate.

Martin Place railway station will also stay shut.