A U.S. Air Force jet with one pilot aboard crashed Monday while supporting American soldiers fighting in Anbar province, a hotbed of Iraq's Sunni Arab insurgency, and U.S. officials were in the process of collecting details.

The F-16CG jet that crashed was supporting coalition ground forces when it went down at about 1:35 p.m. in Anbar, about 20 miles northwest of Baghdad, the military said in a brief statement. The statement had no information about the suspected cause of the crash or the fate of the pilot.

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Mohammed Al-Obeidi, an Iraqi who lives in the nearby town of Karmah, said by telephone that he saw the jet flying up and down erratically before it nose-dived and exploded in a farm field. He said other U.S. warplanes rushed to the crash site and were circling around it.

Maj. Gen. William Caldwell, a U.S. military's spokesman, said he doubted the jet was shot down because F-16s fly very fast and have not encountered weapons in Iraq that are capable of taking them down.

Al-Jazeera satellite television showed videotape pictures of the wreckage in a field and what looked to be portions of a tangled parachute nearby. The broadcaster said the video included scenes of the dead pilot but that they were too graphic to air.

One shot showed what appeared to be the tail number and included the letters CG. The jet that crashed was an F-16-CG, the military said. Another segment showed an Air Force seal that said Air Combat Command.

Meanwhile, mortar rounds crashed into an oil processing facility near the northern city of Kirkuk, igniting a huge blaze.

The fire at the pipeline filtering facility shut down the flow of crude to the massive Beiji refinery to the southwest, according to an official at the North Oil Co., who spoke on condition of anonymity because he was not authorized to talk to reporters. The flames erupted at 6:30 p.m. and burned for several hours before they were extinguished, the U.S. military said.

The facility is 15 miles northwest of Kirkuk, a city which sits amid some of Iraq's richest crude oil deposits.

Earlier Monday, a bomb exploded beneath an oil pipeline south of Baghdad and set it on fire, and Iraqi and American forces were deployed to secure the area, police said.

No injuries were reported in the 7:30 a.m. blast near Mahmoudiya, about 20 miles south of Baghdad, said police 1st Lt. Haider Satar. The fire was put out about noon. The pipeline carries crude oil from storage tanks in nearby Latifiyah to the Dora refinery in Baghdad.

Since the U.S.-led war toppled Saddam Hussein in March 2003, the country's oil industry has suffered many such attacks on its pipelines.

The government fully lifted a curfew on Monday, allowing vehicles back on the roads and reopening the international airport, on the fourth day after suspected Sunni insurgents used bombs and mortars to kill more than 200 people in Sadr City, a large Shiite slum, in the worst attack by militants in the war.

Also Monday, Iraq's parliament speaker implemented new rules banning reporters from the legislative building and imposed a 30-minuted delay on broadcast of sessions, an apparent bid to squelch information reaching the public about the increasingly bitter debates between Shiite and Sunni lawmakers. The delay would allow the speaker to censor debate that he considered overly inflammatory.

The new regulations reflect al-Maliki's contention that Iraq's violence is a result of excessively vitriolic political rhetoric. A particularly bitter debate last week preceded the devastating Sadr City attacks.

Across the country on Monday a total of 91 people were killed or found dead in sectarian violence. Forty-one bodies were found dumped in the capital alone.

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