Officials have confirmed that some emergency workers were among the dead.
Turkish authorities are still investigating two separate road accidents that killed at least 35 people, including emergency workers.
The crashes occurred on Saturday just 250 kilometres apart in southern Turkey.
In the first incident, a bus collided with emergency crews that had responded to a crash in Mardin Province, west of Derik.
Three firefighters, two paramedics and two reporters were among the 15 people killed, according to Interior Minister Suleyman Soylu. Eight of the victims were from the bus, he said.
The Ilhas News Agency said two of its journalists died after stopping to help a car which had come off the road and slid down an embankment.
Gaziantep Gov. Davut Gul said a total of 22 people were also injured in the crash involving the bus.
The other incident happened late on Saturday afternoon in Derik after the brakes of an articulated truck failed, causing it to crash into two other vehicles near a petrol station.
As first responders worked at the scene, another truck lost control and ploughed into the crowds.
Speaking from the site, Soylu said 20 people -- including a police officer -- were killed and 26 injured. Two drivers have been detained as part of the investigation.
Turkey has a poor record of road safety. Some 5,362 people died in traffic incidents last year, according to the government.