An important gas pipeline has been blown up in northern Iraq.
There have been regular attacks on Iraqi infrastructure
The resulting fire was so huge the glow could be seen in the night sky in the town of Kirkuk, 30 kilometres (20 miles) away, say reports.
The attack is expected to cause disruption to production at Iraq's largest oil refinery, officials say.
Amid continuing violence, coalition officials have suspended civilian flights into Baghdad airport after a missile attack on a plane on Saturday.
The Jordanian carrier Royal Wings and DHL courier company have both been ordered to suspend flights.
Together they operated the limited civilian air service to Baghdad.
The ban will remain in place "pending further investigation," coalition military spokesman Brigadier General Mark Kimmitt told a briefing, according to news agency AFP.
Military flights will still operate.
The Kirkuk-based North Oil Company told AFP an explosive device caused the pipeline fire.
The attack has halted supplies of gas from Jambur oil field to a power plant in the town of Baiji.
That in turn is likely to cause disruption to oil production at the refinery in Baiji - Iraq's largest - the head of the oil company's fire department reportedly said.
There have been a number of attacks on Iraqi infrastructure by insurgents against the US-led occupation.
In Baghdad, Brigadier General Kimmitt refused to confirm whether two soldiers killed on Sunday in Mosul had had their throats cut.
"We will not be ghoulish about this," he said.
"We have an ongoing investigation. It is not our policy to discuss the specifics of injuries sustained by soldiers and this is not a good place to discuss these kind of things."
The men, from the 101st Airborne Division, were on patrol in Mosul when their convoy was reportedly fired on.
There is confusion over how two US soldiers died in Mosul
A US military spokesman said the men were shot dead.
However, witnesses said their vehicle crashed and their assailants then slit their throats.
In a separate attack, a US soldier died in a roadside bombing near Baquba, north of Baghdad, US officials said.
The US military has also confirmed that two US soldiers died and one was injured on Saturday, when their armoured vehicle was crushed by an M-1 Abrams tank near Baghdad airport.