Iraqi engineers began repairs Saturday to a northern oil pipeline that has been disabled for months by militant attacks, costing the country millions of dollars in lost revenues, officials said.

The repairs to 40 kilometres (25 miles) of the pipeline, which runs from the northern province of Kirkuk to the Turkish port of Ceyhan, are expected to take between 10 days and two weeks, oil ministry officials said.

"The maintenance started today," ministry spokesman Assem Jihad told AFP.

"You can calculate the losses yourself," he said. "The pipeline has been down since March 2, and 300,000 to 400,000 barrels (of oil) per day have been suspended because of security and a series of attacks targeting the pipeline."

Jihad said security forces had carried out multiple operations against militant groups to ensure access to the pipeline.

He said there was now "a secure environment for technical teams to reach and fix the pipeline, to resume pumping operations without new sabotage."

An official in the state-owned North Oil Company forecast that the repairs would require up to two weeks, and would take place largely between the towns of Sharqat, in Salaheddin province, and Ain al-Jahash, in Nineveh further north.

Iraq is heavily dependent on oil exports, which account for more than 90 percent of government revenue and more than two-thirds of gross domestic product, according to the International Monetary Fund.

Efforts to diversify the economy have stalled, and Baghdad has sought to dramatically ramp up oil exports in a bid to rebuild the country's infrastructure, which has been badly damaged by decades of conflict and sanctions.

But while sales from its southern ports have steadily increased, sabotage has repeatedly hit the Kirkuk-Ceyhan pipeline.

In June 2011, Iraq exported 16.4 million barrels of oil through the pipeline, but that figure has been in fitful decline since, bottoming out last month, when no sales were recorded via Ceyhan.

Exports nevertheless averaged 2.5 million barrels per day in April, after reaching 2.8 million bpd in February, its highest level in decades.

Despite the steady increase in oil exports, many Iraqis complain that much of the windfall is lost to state corruption and that the proceeds have not markedly improved daily life.