Baquba, Iraq: Masked gunmen killed 18 people, most of them Iranians, working on a gas pipeline outside the northeastern Iraqi town of Muqdadiya on Friday, witnesses and officials said.

One worker wounded in the assault said the attackers sped up in three cars as he and his colleagues were digging a trench to extend the line.

“Three of them got out of a car and started firing on the workers inside and outside the trench,” said Ebrahim Aziz by phone from hospital.

No group immediately claimed responsibility for the attack on the workers, 15 of them from Shi’ite Muslim power Iran. But officials said militants from the Iraqi arm of Al Qaida had been active in the area.

Ten years after the US-led invasion that toppled Saddam Hussain, Iraq’s Sunnis, Shiites and Kurds have yet to find a stable power-sharing deal and violence is again on the upswing.

Islamists see neighbour Iran as one of their main enemies, particularly because of Tehran’s support of Iraq’s now Shiite-led government.

Iran signed a deal in July to build a pipeline and import gas into Iraq to fuel power plants in Baghdad and Diyala province, where the attack took place.

Officials said the workers were employed by an Iranian oil and gas company, but did not give its name. The three other people killed were Iraqis and eight workers were wounded, medical and local officials said.

In a separate incident, at least five people were killed and 14 wounded when a car bomb exploded in southern Baghdad’s outskirts of Nahrawan, police said.

A further six people were killed in a car bomb explosion in the town of Madaen, south of Baghdad, police said.