It was not immediately known whether the attack on Thursday night in the Fatha area near the refining centre of Baiji had damaged the Iraq-Turkey export pipeline, which passes through the area, as do 24 crude oil and product pipelines feeding refineries and power stations.
Northern oil exports have been idle since 18 December when saboteurs hit the Iraq-Turkey pipeline. It has been sabotaged several times since.
Another pipeline running from the Kirkuk oilfields to the 350,000 barrel per day (bpd) Baiji refinery was also hit on Friday in the Safra area, officials said.
Attacks against northern oil facilities have escalated in the last two months, cutting off exports to Turkey's Ceyhan port and helping deepen a fuel and electricity crisis.
Dhiaa al-Bakkaa, head of the State Oil Marketing Organisation, said this week exports through Turkey could flow at 250,000 barrels per day if the sabotage stops, compared to 800,000 bpd before the 2003 US-led invasion of Iraq.
Iraq is exporting around 1.6 million bpd from its two terminals offshore in the Gulf.
Officials say repairs to pipelines continue despite risks to workers' lives, but acknowledge that they are facing insurgents determined to disrupt the economy.