Insurgents using explosives set fire to the main oil pipeline in northern Iraq on Thursday, officials said. Violence continued around the country, and the U.S. military said three soldiers were killed by a roadside bomb the previous day.

The pipeline links an oil field in the northern city of Kirkuk (search) to Iraq's largest oil refinery in Beiji, 155 miles north of Baghdad.

The explosion occurred at about 5 a.m. (8 p.m. EDT Wednesday), setting fire to the pipeline and several oil valves about 34 miles west of Kirkuk, said firefighter Adil Mohammed.

"The damage is 100 percent, and we've haven't been able to control the fire yet," he said.

Iraq has the world's third-largest known oil reserves, but the industry has been crippled by several wars, sanctions during Saddam's rule and the anti-U.S. insurgency. Oil production remains limited, curbed by decaying infrastructure and frequent militant attacks on pipelines and refineries.

The three U.S. soldiers killed Wednesday were part of Task Force Liberty (search) 42nd Infantry Division. They were on combat patrol about 7:45 p.m. Wednesday (10:45 a.m. EDT) near Balad, 50 miles north of Baghdad, when the roadside bomb exploded, the military said. A wounded soldier was transported to a Coalition Forces medical facility for treatment.

The military also said a soldier assigned to Regimental Combat Team 2, 2nd Marine Division, II Marine Expeditionary Force (Forward), died from a non-hostile gunshot wound Tuesday at a forward operating base near Mosul (search), 225 miles northwest of Baghdad. The incident was being investigated, the military said, without providing any details.

The fatalities raised to at least 1,987 the number of members of the U.S. military who have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.

That total includes one 42nd Infantry Division soldier who was killed and four who were wounded when their 42nd Infantry Division vehicle was burned by a roadside bomb at about 6 p.m. Wednesday near Tikrit, 80 miles north of Baghdad, the military said.

The names of the soldiers were being withheld pending notification of their relatives.

Among the other scattered violence in Iraq on Thursday:

— At 10 a.m. local time (1 a.m. EDT), militants riding in a car opened fire on civilians outside a food shop in the southern Dora area of Baghdad, killing two, police said. The militants then stopped, rushed into the store and gunned down a third Iraqi, police said.

— At 11 a.m., a rocket hit a public school for students aged 12 to 15 in the western al-Mansour neighborhood of the capital, killing one child and wounding five, police said. A nearby shopkeeper also was killed.

— At noon, a suicide car bomb exploded in front of a provincial government building in the city of Baqouba (search), 35 miles northeast of Baghdad. Three people were killed and 14 wounded, police said.

Also Thursday, Amr Moussa (search), the secretary-general of the Arab League, arrived in Baghdad, his first visit to Iraq since Saddam's ouster in 2003. Moussa is here to discuss plans for an Iraqi reconciliation conference.

Moussa is disliked by many Iraqi Shiite Muslims and Kurds for his perceived refusal to act against Saddam Hussein's persecution of both groups while the dictator was in power. But Moussa was expected to meet with Iraq's most powerful Shiite cleric, Grand Ayatollah Ali al-Sistani (search), and with government and tribal leaders during his three-day visit.

On Wednesday, Saddam and seven senior members of his regime went on trial for a 1982 massacre of about 150 Shiites in the town of Dujail (search), north of Baghdad. Saddam challenged the legitimacy of the court and pleaded innocent to all charges. The judge then adjourned the session until Nov. 28.

On Wednesday, senior Iraqi security officials announced the arrest in a Baghdad apartment of Saddam's nephew, Yasir Sabhawi Ibrahim (search), after Syrian authorities forced him to return to Iraq several days earlier.

The arrest of Ibrahim — the son of Saddam's half brother, Sabhawi Ibrahim al-Hassan al-Tikriti, and a financier of Iraqi insurgent groups — dealt a serious blow to the militants, the officials said on condition of anonymity since they are unauthorized to speak to the media.

Police also provided new information about the kidnapping of Rory Carroll (search), 33, an Irish citizen who is the Baghdad correspondent of The Guardian, the British newspaper.

Police Maj. Falah al-Mohamadawi said Carroll was captured at 3:30 p.m. Wednesday in the Sadr City (search) section of the capital. The officer said gunmen riding in two cars blocked a road and snatched Carroll from his car, leaving his driver behind.

A search was under way for the captive, said al-Mohamadawi.