KIRKUK, Iraq, Sept 2 (AFP) - Three Turkish hostages were reported killed by Al-Qaeda linked insurgents in Iraq but France voiced optimism Thursday that its abducted journalists would soon be freed, saying they were safe and well.
In the north, vital oil exports were halted after saboteurs set ablaze part of a pipeline in what officials said was the largest ever such attack, sending thick clouds of smoke over the city of Kirkuk and some residents fleeing.
The renewed violence came after 20 people were killed in an overnight US air strike in the rebel hotbed of Fallujah targeting suspected Al-Qaeda operative Abu Mussab al-Zarqawi.
Three Turkish truck drivers were reportedly killed by members of a group linked to Zarqawi in a jarring reminder of the high stakes for the still captive French journalists -- Le Figaro reporter Georges Malbrunot and Radio France correspondent Christian Chesnot.
Arabic-language satellite television Al-Jazeera said it had received a video showing the execution of three Turkish hostages by the Tawhid wal Jihad group which also threatened to kill more foreigners and warned: "The time for mercy is over."
Police and medical officers in Iraq told AFP that three Turkish truck drivers were found shot dead on the roadside outside the rebel den of Samarra north of Baghdad, apparently the hostages.
On Tuesday, hostage-takers in Iraq released a video and statement announcing the killing of 12 Nepalese. It was the largest massacre of foreign hostages in the country and the gruesome footage sparked a rampage by angry protestors in Kathmandu.
But the French were holding out hope Thursday that the fate of the two French journalists would be different.
"They are alive, in good health and well treated," Ambassador Bernard Bajolet told AFP. "That is the information we have received today."
His comments came after the French Council for the Muslim Faith (CFCM) flew to Baghdad on a lightning mission to help save the journalists who were kidnapped on August 20 by an extremist group known as the Islamic Army of Iraq.
The delegation departed after saying they were reassured about the fate of the journalists following talks with the influential Council of the Muslim Ulema, an association of conservative Sunni clerics that has intervened in previous hostage crises.
"We leave with confidence and full of hope," delegation chief Abdullah Zekhri told AFP.
The news emerged even as France went ahead Thursday with implementing a controversial ban on the Islamic headscarf in state schools despite demands by the kidnappers to change the law.
In Kirkuk, smoke billowed across the oil rich city after the pipeline blast, which came barely two weeks after the pipeline resumed production to the Turkish port of Ceyhan following months of sabotage attacks.
"The pipeline with Turkey was shut down," said Ahmed Hassan Ghafif, head of the Northern Oil Co's security for gas and oil pipelines.
Ghafif called it the largest strike against the north's oil infrastructure and the smoke and fire cut off the road between Kirkuk and Baiji.
He predicted it would take two to three days to douse the blaze and gave no estimate on when the pipeline would resume pumping its average of 600,000- 800,000 barrels of oil per day to Turkey.
The pipeline was at full production when the bomb exploded at 6:30 pm (1430 GMT) near the town of Riyadh, 50 kilometres (30 miles) south of Kirkuk, according to Ghafif and Kirkuk national guard chief Major General Anwar Hamid Amin.
Repeated sabotage of Iraq's oil industry has cost the country more than a billion dollars in revenue.
Elsewhere, US jets struck the city of Fallujah overnight in a raid targeting hideouts suspected of belonging to the Jordanian-born al-Zarqawi, wanted by the United States for a string of attacks and kidnappings.
Two buildings were destroyed and rescue workers had pulled 20 bodies from the rubble by Thursday morning.
The US military described the attack as a "precision" strike on "safe houses and meeting locations" for associates of Zarqawi.
In Baghdad, US troops patrolling the streets of the Shiite rebel bastion of Sadr City called on fighters from Moqtada Sadr's Mehdi Army to turn in their heavy weapons after the firebrand cleric called for a truce.
None of the militiamen in the sprawling Baghdad slum could immediately be seen handing over their rocket-propelled grenade launchers or mortars but a surprise ceasefire ordered by Sadr on Monday has so far been observed.
An aide to Sadr told AFP no deal had been reached yet to set up collection points throughout the Baghdad slum but added that a last round of talks to that purpose was due to be held on Thursday night.