Iran issued an advisory warning its citizens Saturday to avoid land travel to neighbouring Turkey after an Iranian bus was attacked by gunmen.
No one claimed responsibility for the attack but Turkish authorities blamed Kurdistan Workers' Party (PKK) militants.
"Based on recent movements and insecurity in Turkey's east, the foreign ministry advises our citizens travelling to Turkey to avoid land routes until further notice and to use air routes," a foreign ministry travel advisory read.
The Iranian bus was hit on Friday morning in Dogubayazit district of the eastern Agri province. The driver was fatally shot in the head.
The passengers were unhurt, Hossein Ghassemi, Iran's consul in Erzerum, Turkey told Iranian state television Saturday.
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Turkish President Recep Tayyip Erdogan ordered in late July air bombing of Islamic State group jihadists in Syria and also PKK fighters based in northern Iraq.
Turkey's air strikes followed a series of attacks inside its territory including a devastating suicide bombing blamed on IS.
Turkey has since suffered multiple attacks.
On July 31, Iran suspended train services to Ankara after two bomb blasts on the railway in eastern Turkey.
And a bomb exploded last month on the Iran-Turkey gas pipeline, leading to a days-long delay in the transport of gas in Agri province.
The PKK has said a truce with Ankara that had largely held since 2013, while peace talks were ongoing, has been rendered meaningless by Turkey's air strikes in northern Iraq.