Ten police officers were killed in a bomb attack on a minibus in a Turkish province bordering Armenia and Iran, a government official told Reuters, the edge of a region beset by violence between Kurdish militants and the Turkish state.
There was no immediate claim of responsibility for the bombing in the province of Igdir, but it comes after months of attacks by Kurdistan Workers Party (PKK) militants on soldiers and police officers in Turkey's largely Kurdish southeast.
More than 40 Turkish warplanes hit PKK targets in northern Iraq overnight, where the group has bases, in response to the killing on Sunday of 16 soldiers near the Iraqi border, the deadliest attack since a two-year ceasefire collapsed in July.
A security source said scores of PKK fighters were killed in the bombing raids. The PKK, which launched a separatist insurgency in 1984, is designated a terrorist organisation by Turkey, the European Union and United States.
The renewed conflict, weeks before polls the ruling AK Party hopes will restore its majority, has shattered a peace process which President Tayyip Erdogan launched in 2012 in an attempt to end the insurgency, which has killed more than 40,000 people over three decades.
It has also complicated Turkey's role in the U.S.-led fight against Islamic State. A Kurdish militia allied with the PKK has been battling Islamic State in northern Syria, backed by U.S. air strikes. But Turkey fears territorial gains by Syria's Kurds will fuel separatist sentiment among its own Kurdish population.
Dozens of F-16 and F-4 jets took part in the air operation in northern Iraq, which began around 10 p.m. (1900 GMT) on Monday and continued for six hours, the security source said.
The air strikes targeted areas around the PKK's bases in Qandil, Basyan Avashin and Zap, and hit weapons and food stores as well as the militants' machinegun positions.
The Igdir attack came as police travelled in a minibus to a border gate linking Turkey to the autonomous Nakhchivan enclave, sandwiched between Armenia and Iran and controlled by Azerbaijan, the Dogan news agency reported.