A suicide bomber detonated an explosive-laden vehicle at a checkpoint, targeting civilians and security personnel.
A suicide car bomb attack outside a gendarmerie station in southeastern Turkey left 10 soldiers and eight civilians dead and scores of others injured on Sunday.
"The attack was perpetrated by a suicide bomber who detonated a van with five tonnes of explosives," Prime Minister Binali Yildirim told a press conference in Istanbul.
According to Anadolu Agency, the attack was carried out at around 9:45am (06:45 GMT) at a checkpoint in front of the gendarmerie outpost around 20 kilometres (12 miles) from Semdinli town centre in Hakkari Province.
The blast left a gaping hole in the road which was 10-15 metres wide (33-49 foot) and up to seven metres (22 foot) deep, Anadolu said.
Earlier, a statement from the Turkish military blamed the PKK terrorist organisation for the attack. Hakkari Province, which borders Iraq and Iran, has seen a large number of PKK attacks since the group resumed its armed campaign in July last year.
Deputy Prime Minister Numan Kurtulmus described the incident as an "atrocious" and "heinous terrorist attack," vowing on Twitter that Turkey would never surrender to militant groups.
Tm milletimize basal diliyorum. Trkiye terr rgtlerine asla teslim olmayacaktr. Bu menfur saldrlarn hesab sorulacaktr.— Numan KURTULMU (@NumanKurtulmus) October 9, 2016