At least six people were killed and 15 others injured on Wednesday in an explosion at a chemical factory in southeastern Turkey, the local mayor said.

"Six workers were blown up," Asim Guzelbey, mayor of Gaziantep province where the incident took place, said in televised remarks, amid fears that the number of dead could increase.

"Firefighters are still trying to put out the flames," Guzelbey told the NTV news network.

The cause of the blast at the factory in an industrial park near the Syrian border was not immediately clear and the mayor said an investigation had been launched.

Factory explosions are frequent in Turkey.

Last year, an explosion triggered by an accidentally dropped hand grenade killed 25 soldiers at an ammunition depot.