P K Singh, running a hardware shop at Thrissur in Kerala, was coming to the city for buying some things when the gang stopped him near Madukkarai on the National Highway around 4.30 am, they said.
They threatened him with a knife and robbed him of the money and two mobile phones. They then sped away in his car.
Singh, who suffered injuries on the neck in the melee, managed to inform police with the help of locals. A case has been registered and further investigations are on, the police said.