Duty officer of Fire Service and Civil Defence Control Room Russell Ahmed said the first bus was torched in front of the Madhumita Cinema hall at 12:35pm. The second bus was set afire beside the Pir Yamini Market at 1:30pm.
Another bus was torched beside Katabon in Shahbagh area and another at Shahjahanpur of Khigaon at 1:47pm.
Later, at 2:02pm, another bus was torched in front of the secretariat and the sixth one was burnt at Naya Bazar area around 2:28pm.
Several units of firefighters extinguished the flames.
Dhaka Metropolitan Police (DMP) Deputy Commissioner (public relations) Walid Hossain said the arson attacks might be election related violence.