The powerful blast occurred overnight at a section of the pipeline near the eastern Turkish town of Dogubayazit, in Agri province, several kilometres (miles) from the Iranian border, a local official told AFP by telephone, without giving other details.

"The explosion is believed to have been carried out by members of the separatist terrorist organisation," Agri Governor Ali Yerlikaya said in a statement, using officialese for the outlawed Kurdistan Workers' Party (PKK).

Security forces are looking for the perpetrators, said the statement, carried by Anatolia news agency.

Television footage showed a large blaze raging over the pipeline after the blast, which, Anatolia said, shattered the windows of nearby buildings.

The PKK has dramatically stepped up its 26-year separatist campaign since its jailed leader Abdullah Ocalan said through his lawyers in May he was abandoning efforts to seek dialogue with Ankara.

The explosion cut the flow of Iranian gas, but an official at Turkey's state oil and gas company BOTAS ruled out a supply shortage, saying that gas coming via pipelines from Russia and Azerbaijan was meeting the needs.

"There is no problem at the moment," she told AFP.

Repairs at the damaged section of the Iranian conduit were expected to take about a week, she said, adding that the fire had been extinguished as of Wednesday morning.

Earlier this month, PKK militants were blamed also for a blast that hit a pipeline carrying oil from Iraq in southeastern Turkey.

In one of their bloodiest assaults this year, the rebels targeted a military unit near the Iraqi border Tuesday, killing six soldiers.

The PKK, listed as a terrorist group by Ankara and much of the international community, took up arms for self-rule in Turkey's Kurdish-majority east and southeast in 1984, sparking a conflict that has claimed some 45,000 lives.