A total of 51 people, including 23 civilians were also injured in the incident, according to the source, who spoke to Anadolu Agency on condition of anonymity due to restrictions on speaking to the media.
One of the slain police officers was six-months pregnant when she was pronounced dead at a local hospital.
The source added that the other police officer martyred in the blast was also a woman. She died at the scene in Midyat, a town in Mardin province, alongside three civilians.
The two officers were on duty at the entrance to the police station when the explosion hit at around 11 a.m. local time (0900GMT), causing heavy damage to nearby buildings.
A security source told Anadolu Agency that the PKK terrorist organization was responsible for the attack.
Mardin is among the southeastern provinces that have seen heightened PKK activity since the group - listed as a terror organization by Turkey, the U.S. and EU - resumed its armed campaign in July last year.
During that period, around 500 security personnel have been martyred and more than 4,900 PKK terrorists killed in operations across Turkey and northern Iraq.