A Melbourne tradesman has spoken about his terrifying ordeal when three men posing as undercover police officers dragged him from his car and bashed him in an attempted robbery.

Reservoir landscaper Mohamed Dirini, 24, was in his grey Holden Rodeo utility driving west down Wood Street on the way to buy a present for his wife when he saw a car following close behind.

Police believe the car - a dark Commodore sedan - had fake police lights fixed to the dash.

Detectives allege the men flashed the lights to pull over Mr Dirini, 24, who was driving along Wood Street in Preston about midday on June 9.