The accidents took place on Friday.
Eight passengers of a microbus were killed and three others injured in a collision between a bus and a microbus in Bijaygnagar area in the morning.
Of the deceased, seven were identified as Habibur Rahman, his sons Abu Sufian and Md Kamran, their relatives Morshedur Rahman, Alin Hassen, Abdul Hannan and Mokter Mia.
Bijaygnagar OC Ali Ershad said: “Seven people dead on the spot.”
Five people were killed and 21 others injured as a bus turned turtle in Pungli area under Kalihati upazila.
The deceased are Asma Begun, 40, wife of Firoz Mia of Lalmonirhat, Asadul Habib, 15, son of Abbas Ali, Ripon, Shumon 25, and Monirul, of Lalmonirhat
Elenga highway police outpost Sergeant Jahangir Alam said: “A Dhaka-bound bus truned turle when its driver lost his control over the steering in Pungli area around 4:15am on Friday, injuring 25 people.”
Tangail Medical College Hospital Emergency Medical Officer Towhid said five of the injured died when taken to the hospital.
Four people were killed and 15 others injured as a bus hit a three-wheeler, locally named Mahendra, on Dhaka-Barisal Highway in Rajoir area of Madaripur around 12pm.
The deceased could not be identified immediately.
Police said, two of them died on the spot and two succumbed to injuries at Rajoir Upazila Health complex.