Iranian gas flow to Turkey has been halted due to an explosion on the pipeline in Turkey overnight and repairs have been started which will take one week, a Turkish Energy Ministry official told Reuters on Friday.

"Repairs have been started on the Turkey-Iran pipeline. The repairs and restarting of gas flows will take one week," the official told Reuters.

He said Turkey was buying additional gas from Azerbaijan and Russia to cover the shortfall caused by the explosion, which according to state-run Anatolian news agency occurred in the eastern Turkish province of Agri.

Iran is Turkey's second-biggest supplier of natural gas after Russia, sending 10 billion cubic meters of gas each year. Turkey uses gas to fire half of its power plants.

It was not immediately clear what had caused Friday's blast but sabotage is common on pipelines leading into Turkey from Iran and Iraq, where Kurdish separatist militants operate.

Late last month, gas exports from Iran to Turkey were briefly halted due to a blast. The pipeline was swiftly repaired and gas flows were resumed a day later.

The Kurdistan Workers' Party (PKK), a separatist Kurdish militia, has claimed two separate attacks on the pipeline on Aug 3.