Two big bike riders died after their motorcycles collided and were then run over by an 18-wheeler in Phetchaburi's Khao Yoi district on Sunday morning.

Police said a woman, 22, and a man, 27, were riding their motorbikes in a group of more than 100 motorcyclists when the accident happened in front of a PTT petrol station on outbound Phetkasem Road in tambon Huay Rong at about 8am.

Witnesses said the bike riders spread across three traffic lanes and were riding at high speed, with some overtaking others from both the left and right sides. At one point, the victims' motorcycles grazed one another and both fell off their bikes.

They were hit by an 18-wheeler lorry behind them and died at the scene. The truck's driver fled the scene of the accident. Another motorcyclist was injured in the crash and was sent to Khao Yoi Hospital.