GAZIANTEP, Turkey, May 1 (UPI) -- Two Turkish police officers were killed in a bombing in police headquarters Sunday morning in the southern province of Gaziantep, a local governor said.
Also, at least 18 other police officers and four civilians were killed in the suspected car bombing.
Two cars entered the area and fired with automatic weapons, local media said. One car escaped after police fired back and the second one exploded.
"We've reached significant information, but the Interior Ministry will make the necessary statement in due course," Prime Minister Ahmet Davutoglu said.
Gaziantep's International Worker's Day celebrations were canceled after the bombing.
Gaziantep, with a population of 1.5 million, is about 34 miles from Islamic State-controlled territory along the Syrian border.
Last month, the United States warned of "credible threats" to public areas in Istanbul, the same day a flash grenade went off near a bus station, injuring three people.