In the first accident, two labourers were killed in Bhnaga upazila at about 10:30am.
The deceased were identified as Milon Molla, 26, and Chan Mia, 35, hailed from Shibchar in Madaripur.
Local sources said a truck hit another one in Puliabazar area, leaving a labourer dead on the spot and another at the upazila health complex.
In another accident, three people were killed when a bus of eagle Paribahan hit hard a roadside tree in Dhuldi area under Sadar upazila at about 11am, leaving three dead on the spot and 15 injured.