A counter-terrorism operation is under way in Melbourne related to Monday's deadly Brighton siege, Victorian Premier Daniel Andrews says.
A witness said at least 20 police were "running around" on a major road, including Special Operations Group officers.
"They are running around like mad," a caller to 3AW said.
"They're in transit but they must be close because they're running."
Fairfax Media says witnesses reported seeing federal and Victorian officers searching rubbish bins before 6am.
The operation is being conducted around Ascot Vale.
Mr Andrews said the Friday morning raids are connected to Monday night's Brighton siege in which Melbourne man Yacqub Khayre shot and killed Chinese-born Kai Hao and held an escort hostage before dying in a hail of bullets.
"A number of warrants are being executed in Melbourne as we speak," Mr Andrews told Sky News.
"We're obviously limited in what we can say, we don't want to put any of our operational staff in harm's way by speaking about these matters, but they are in connection with the terrible tragic events of Monday in Brighton."
Police would not comment about the operation while it was ongoing.
"Victoria Police and their partners within the Joint Counter Terrorism Team are conducting a police operation in the northern suburbs this morning," Victoria Police said in a statement on Friday.
"As this relates to an ongoing investigation, it is not appropriate to comment further."
