The gang, wearing balaclavas and armed with baseball bats, ambushed and robbed five taxis in separate incidents in Sunshine, Brooklyn and Laverton North areas on Saturday night.
They pulled up in two stolen cars and attacked the drivers.
"This is absolutely disgraceful, and these shocking attacks on cabbies are nothing but disgraceful," Baillieu said in a statement.
Harpreet Singh, 30, was driving his taxi through Sunshine suburb when his car was rammed from behind and a second car pulled up abruptly in front of him.
He said four men with baseball bats got out of the car in front of him and began smashing the driver-side window.
Yesterday, police arrested eight teenagers in connection with the spate of violent armed robberies targetting taxi drivers. The youths, aged between 14 and 18 including one female, were arrested after a series of police raids.
Meanwhile, state government also announced that it would examine every opportunity to support taxi drivers and their safety.