Two civilians and a police officer died in the attack on police headquarters in the town in Mardin province, Prime Minister Binali Yildirim told reporters.
The blast wounded 30 people, who were taken to nearby hospitals, he said, adding that the toll would likely have been higher if it were not for barriers in front of the building.
He blamed the banned Kurdish separatist PKK group for the attack, saying: "We are not surprised by this, but the circle is tightening around them."
Turkish jets hit PKK targets in Iraq and southeastern Turkey on Tuesday, state-run Anadolu news agency reported, citing military officials.
Second car bomb attack in 2 days
The attack targeted a police bus traveling through the bustling Beyazit neighborhood of Istanbul's historic Fatih district during morning rush hour.
Four people were detained Tuesday in relation to that attack, which also injured 36 people, authorities said.
Funerals for the dead were held Wednesday. Yildirim and former President Abdullah Gul attended a service for two of the officers.
Turkey has weathered a string of terror attacks over the past year as it faces the twin threats of ISIS and Kurdish militants.
As part of the U.S.-led coalition against ISIS, Turkey allows coalition planes to fly raids on ISIS targets in neighboring Iraq and Syria from its territory.
And last year Turkey resumed hostilities with the PKK in earnest after a two-year cease-fire broke down.
Since then, Anadou reports, about 500 Turkish security forces and about 4,900 PKK members have been killed in the conflict.
The PKK, or Kurdistan Worker's Party, is considered a terror group by Turkey, the United States and the European Union, and has been in an armed conflict with Turkey for decades.
Attacks in recent months include a bombing near a bus stop in the capital, Ankara
in March in which at least 37 were killed. The attack was claimed by a Kurdish militant group.
Six days later an ISIS suicide bomber struck in Istanbul, killing four.
A month earlier, 28 were killed in a blast targeting military vehicles in central Ankara
, claimed by a Kurdish group.
And in January, at least 10 German tourists died in an ISIS suicide bombing in Istanbul's Sultanahmet Square
The violence has had an impact on Turkey's tourism industry, a key sector of the national economy.