TEHRAN, Aug. 8 (Xinhua) -- Iran issued an advisory on Saturday warning its citizens to avoid land trips to Turkey following a recent terrorist attack on an Iranian bus in the country.

Due to the insecurity in the eastern part of Turkey, the Iranian foreign ministry advises its citizens to travel to Turkey by air and avoid land trips until further notice, Iran's foreign ministry said.

An Iranian passenger bus was attacked by gunmen on Friday in Turkey's eastern Agri province. The bus driver was killed and three passengers were injured.

No group has claimed responsibility for the attack but Turkey has blamed the outlawed Kurdish Workers' Party (PKK) militants of recent attacks in the eastern Turkey.

In July, an Iranian passenger train was also hit by a landmine in Turkey but nobody was hurt.

Last week, Iran resumed its natural gas flow to Turkey after a week of halt when an explosion hit the pipeline inside Turkey.