Rescue and emergency responders work at the scene after a bus crash on the highway between Gaziantep and Nizip, Turkey, on Saturday. Reuters

Sixteen people including emergency workers and journalists died when a bus crashed into an earlier accident site, regional governor Davut Gul from southeastern province of Gaziantep said. Another 20 people were wounded and received treatment.

"At around 10:45 this morning, a passenger bus crashed here," Gul said, speaking from the scene of the accident on the road east of Gaziantep.

The DHA news agency said a passenger bus had crashed into an ambulance, a firefighting truck and a vehicle carrying journalists at the site of a previous crash.

"Three firefighters, two emergency workers and two journalists figure among the dead," the Gaziantep governor said. Photos on DHA showed the back of an ambulance ripped out and metal debris strewn around it.

"While the fire brigade, medical teams and other colleagues were responding to the accident, another bus crashed 200 metres behind. The second bus slid to this site and hit the first responders and the wounded people on the ground."

Separately, a truck hit a site some 250km east in Derik district of Mardin where first respondents were attending to another accident, according to footage.

People gather at the site of the second accident in Mardin. Twitter photo

Sixteen people died and 29 others were injured as a result of the incident in Mardin, Turkish Health Minister Fahrettin Koca said, adding that eight of the wounded were in critical condition.

The accident in Derik in Mardin province "occurred after the breaks gave out on a lorry, which hit a crowd," Koca said on Twitter.

Turkish media shared footage of a driver losing control of his truck, then careening towards nearby vehicles and pedestrians trying to flee.

Türkiye 's official Anadolu press agency said an accident involving three vehicles had happened at the same site shortly before, and emergency responders were already at the scene when the lorry ploughed into crowd.