Two buses were set on fire in Dampara and Akbar Shah areas of Chattogram city on Sunday night.
A helper of another bus sustained burn injuries when he was trying to douse the flame in Dampara area.
The incident happened when the opposition parties are observing their 48-hour blockade programme across the country.
Injured helper Md Nazim Uddin said that 10 to 12 youths carrying torches showed up at a ticket counter of Saudia Paribahan in Dampara area around 10pm.
A double decker belonging to 'Relax Paribahan' was parked in front of the counter. The men with torches broke the glass of the bus and set fire to it. Later, instantly left the scene.
The helper's right hand was burnt when he tried to douse the fire.
Khulshi Police Station's Officer in-Charge Rubel Hawlader said they were trying to identify the arsonists.
Miscreants also set fire to a parked bus on the Dhaka-Chattogram Highway in Akbar Shah area around 9:35 pm on Sunday.
On information, two firefighting units rushed to the spot and doused the flame immediately, said deputy assistant director of Fire Service and Civil Defence department (Agrabad division office) Md Abdur Razzak.
No one was injured in the incident.
TF