The bomb, which went off near a wedding celebration in the town of Semdinli, targeted an armoured police vehicle, the prime minister said.
Eighteen people were also injured.
No group has said it carried out the attack, but Mr Erdogan blamed the Kurdish militant movement, the PKK.
It has attacked military checkpoints and convoys, and carried out bombings in cities. Some 40,000 people, including civilians, have died in the conflict.