BAGHDAD – Mortar shells slammed into an Interior Ministry prison Monday, killing at least five inmates and wounding 25, the U.S. military and Iraqi officials said. Separately, a fire broke out at one of Iraq’s main refineries, but the U.S. said it was an industrial accident – not an attack, as Iraqi officials insisted.

Police and hospital officials said seven inmates were killed and 23 wounded when the mortar rounds hit a prison made up of several cellblocks, each containing prisoners accused of terrorism-related crimes or civil offenses. The U.S. military said five inmates died and 25 were injured.

Police said American troops sealed off the area around the main Interior Ministry compound on the east bank of the Tigris River in central Baghdad. The rounds struck about 200 yards from the main ministry building.

A hospital official said the inmates were sleeping when the mortar rounds hit, one landing directly on a cell and two others nearby. Casualties were sent to a hospital inside compound for treatment, the official said, speaking on condition of anonymity because he was not authorized to release details of the attack.

Black smoke billowed for hours after the fire broke out at the Dora refinery, which was built in the 1950s and is the country’s oldest. One of three main refineries in Iraq, the Dora facility – like most of the industry – is operating at half capacity because of pipeline attacks since the 2003 U.S. invasion, said Oil Ministry spokesman Assem Jihad.

He said he could not comment on the latest information from the U.S., but said when he was at the refinery earlier, officials there had confirmed an attack.

The U.S. military initially said the southern Baghdad plant came under indirect fire, the military term for mortars or rockets, but later said American forces had determined that the fire “was the result of an industrial accident.”

The military said Iraqis and Americans arrived at the refinery shortly after the fire broke out about 9 a.m. and began to get the situation under control.

Later Monday, an official with the Interior Ministry said a mortar attack caused the fire. The official spoke on condition of anonymity because he was not authorized to released the details.

Jihad said the plant was still operating and the fire would not affect production. He said a few firefighters and a refinery employee suffered from breathing problems after trying to extinguish the blaze.

Iraq’s oil industry has come under repeated attack since the war began, including on Friday when a bomb exploded beneath a key pipeline outside the northern city of Beiji, home to the country’s largest refinery.

According to Oil Ministry figures from July, the industry suffered 159 attacks in 2006 by insurgents and saboteurs, killing and wounding dozens of employees and reducing exports by some 400,000 barrels a day. Such attacks have cost Iraq billions of dollars since the 2003 U.S. invasion.

Foreign Minister Hoshyar Zebari, meanwhile, said a new security pact with the United States would set a time limit on the American troop presence, saying the government’s eventual goal was “to reach a level of preparedness that leaves us with absolutely no need for foreign forces to remain in the country.”

He said Iraq had formally requested U.N. authorization for the U.S.-led presence in Iraq.

“We left an underline that the Iraqi government hoped that this would be the last extension of the mandate,” he said, adding the negotiations for a new pact with the U.S. would be “the most important that Iraq has ever entered.”

He said the deadline for reaching an agreement was July: “There will be negotiations about the conduct of these (U.S.) troops and their rights, privileges and also questions of command and control.”

Zebari also said U.S. and Iranian experts would meet Dec. 18 to discuss security issues ahead of an expected round of formal talks on Iraq’s stability. He said both sides agreed to a fourth round of ambassador-level talks in Baghdad, but the timing was under discussion.

Previous sessions ended inconclusively with Iran rejecting U.S. allegations that it supports Shiite insurgent groups in Iraq by providing bomb-making materials responsible for the deaths of American troops.

Violence has declined sharply in Iraq since June, when the influx of U.S. troops to the capital and its surrounding areas began to gain momentum. Baghdad has seen some of the most dramatic improvements, but roadside bombings, suicide attacks and mortars persist.

On Monday, a roadside bomb targeting a police patrol in eastern Baghdad killed one policeman and injured five other people, police and hospital officials said.

And on Sunday, in a Shiite region about 60 miles south of Baghdad, a roadside bomb struck a convoy carrying a popular police chief with a reputation for cracking down on militias and resisting pressure from religious and political groups to release favored members.

Hundreds marched along dusty roads to mourn Maj. Gen. Qais al-Maamouri, the police chief of Babil’s provincial capital of Hillah, chanting and firing guns into the air.

At least two Islamic militant Web sites on Monday called al-Maamouri a brutal, anti-militant figure and broadcast old audio clips of the slain al-Qaida in Iraq leader Abu Musab al-Zarqawi describing him as “God’s enemy.”

“We swear to God that no one like him can remain alive,” said al-Zarqawi, who was killed in a U.S. airstrike in 2006.

Also Sunday, a roadside bombing killed three Americans working in Iraq as contractors, the military said. The three were identified as Michael B. Doheny, 35, of Omaha, Neb.; Steven Evrard, 36, of Arlington, Texas; and Micah Shaw, 32, of Vancouver, Wash.

Associated Press writer Hamid Ahmed contributed to this report.