A survivor has been admitted to the 250-bed Kushtia General Hospital in critical condition.
Police said the victims, except the driver, are mentally challenged.
Kushtia Islami University Police Station’s in-charge Mostafijur Rahman Roton said the ambulance from Pabna was heading to Jashore.
A truck of BADC crashed into the ambulance at 11 Mile Laxmipur area, killing five people, including the ambulance driver, on the spot and injuring another man.
Police said the identities of the victims could not be known immediately.
The driver of the truck and his assistant could not be apprehended. A case is yet to be filed over the incident.
Also read: 2,329 killed in 2,159 road accidents over 6 months: SCRF report