The blast late Saturday ripped through a section of the Kirkuk-Ceyhan pipeline near Midyat, in Mardin province, sparking a fire, the source, speaking on condition of anonymity, said. The blaze was put out early Sunday.

Militants from the Kurdistan Workers' Party (PKK) were believed to have bombed the pipeline, and a security operation was underway in the area, added the source.

There was no immediate claim of responsibility from the PKK.

The 970-kilometre (600-mile) pipeline runs from Iraq's northern oil hub of Kirkuk to the port of Ceyhan on Turkey's Mediterranean coast, from where the crude is shipped to world markets by tanker.

The twin conduit, first inaugurated in 1976, carried 167.6 million barrels of oil last year, according to Turkish statistics.

The PKK, listed as a terrorist group by Turkey and much of the international community, has sabotaged the pipeline several times in the past as part of its armed campaign against the Ankara government.

The pipeline has also been repeatedly attacked by Sunni Arab insurgents inside Iraq since the US-led invasion of the country in 2003.

The Turkish source said that PKK rebels also attacked a military unity in Beytussebap town in the neighbouring province of Sirnak late Saturday, triggering a firefight that left two militants dead.

The clash also wounded two civilians and two village guards -- members of a Kurdish militia force paid and armed by the government to assist security forces in their fight against the PKK, he added.

Security forces were scouring the area for the attackers.

The fresh violence comes at a time when the PKK has significantly escalated attacks against Turkish targets after jailed rebel leader Abdullah Ocalan said in May that he was abandoning efforts for peace with Turkey and the rebels called off a unilateral truce earlier this month.

In their bloodiest attack in two years, the PKK killed 12 soldiers last month in an attack on a border unit at the Iraqi frontier, while five soldiers and a teenager were killed in a bomb attack in Istanbul claimed by the rebels.

Five members of the security forces and 12 rebels were killed in clashes inside Turkey on Thursday, which prompted a Turkish air strike on the rebels' rear bases in northern Iraq.

The PKK took up arms for self-rule in Turkey's mainly Kurdish southeast in 1984, sparking a conflict that has claimed some 45,000 lives.