According to Hanoi fire and rescue police, the incident occurred at around 9.51 am near 45 Ly Thuong Kiet Street in Cua Nam Ward while the bus was travelling through the area.
Firefighters from Area No. 7 were dispatched to the scene with multiple fire engines to extinguish the blaze and conduct rescue operations.
Videos circulating on social media showed flames rapidly engulfing the vehicle as bystanders alerted emergency services.
The fire was brought under control at around 10.10 am.
The cause of the fire remains under investigation.