The incident took place on Hisar-Chandigarh road when the four friends were coming towards Gaibipur village late last night after attending a function, police said.
When they reached near the village, an unidentified vehicle hit their bikes, they said, adding that all four were seriously injured.
They succumbed to their injuries when they were brought to civil hospital in Hisar in an ambulance, police said.
A case has been registered against the driver of the unknown vehicle, who fled from the spot and efforts are on to nab the accused, police said.
