Melbourne commuters are facing significant delays after a police operation at Flinders Street Station shut down all rush hour services.

Customers on the network have been urged to “look for alternative modes of transport” as officers four Platforms at the train station evacuated to conduct “checks”.

The train lines were interrupted for about an hour, causing commuter chaos, as well as many workers returning to city offices.

Images posted online showed how heavily armed police officers entered the station, which has since been declared safe.

Metro Trains warned that despite explaining the incident, there would still be “major delays” in all services will be major delays in recovering from an earlier Victoria Police request, “the company said in a tweet.