A mass grave containing the remains of 12 people, including a paramedic who disappeared more than a year ago, was unearthed in in an area long controlled by Al Qaeda in Iraq, officials said Monday. In the capital, an Interior Ministry aide was gunned down in his car, police said.

Two of the decomposed bodies were beheaded, according to an official at Fallujah General Hospital, where the bodies were taken after their discovery on Sunday. Hospital officials, who spoke on condition of anonymity because they were not permitted to release details of the discovery, said some appeared to have been killed as recently as four months ago, and some of the deaths dated to 18 months ago.

Along with the bodies was a Health Ministry card that belonged to the missing paramedic, according to footage from AP Television News.

Iraqi troops unearthed the bodies Sunday afternoon near Lake Tharthar, a man-made body of water about 100 kilometers (60 miles) northeast of Baghdad that has been the site of several mass graves found in recent months. Since ousting extremists in some of the country's most violent areas, Iraqis from both Islamic sects have stepped up their patrols for the missing, leading to more discoveries.

In November, two other mass graves were found near the lake, one containing 40 bodies and another with 29 bodies. Elsewhere last month, a grave containing 17 corpses was unearthed near Baqouba, 55 kilometers (35 miles) northeast of Baghdad. Officials said at the time the bodies were likely those of people seized at fake checkpoints and murdered because of their sectarian affiliation.

U.S. Deputy Secretary of State John Negroponte on Sunday pressed leaders of Iraq's religious and ethnic factions to take advantage of recent security gains to push through legislation aimed at cementing national reconciliation or risk a return to greater violence.

""If progress is not made on these fronts we risk falling back to the more violent patterns of the past," Negroponte said at a news conference in Baghdad.

The U.S. military has said violence in Iraq has fallen to lows not seen since January 2006, but top American commanders have warned that Sunni and Shiite extremists still pose a serious threat.

In Baghdad, gunmen in two cars fired on a Sunni Interior Ministry aide, the Maj. Gen. Fauzi Hussein Muhammed, as he returned home, killing him and wounding his driver, police said. They spoke on condition of anonymity because they were not authorized to release details of the attack. The Interior Ministry could not immediately be reached for comment.

And the mutilated bodies of four guards at an oil facility who were kidnapped at a checkpoint on their way back from vacation were found north of Baghdad on Monday, said Col. Khali al-Zubaie, a spokesman for the Iraqi army in Kirkuk. A fifth man who disappeared with them remained missing, he said.

Political progress has been elusive, with lawmakers clashing over Kurdish oil deals with foreign companies and a draft bill that would allow thousands of former members of Saddam Hussein's Baath party to return to their government jobs. Both measures are among the 18 benchmarks set by U.S. President George W. Bush's administration to encourage reconciliation.

Oil Minister Hussain al-Shahristani, using unusually strong language, told Iraqi state television late Sunday that the contracts signed by the self-rule Kurdish region were illegal.

"Oil is the business of the federal government and any attempt at extracting oil without the approval of the federal government is tantamount to smuggling," he said.

Jamal Abdullah, a spokesman for the regional government of Iraqi Kurdistan, said al-Shahristani's comments were unwarranted: "No one has the right to slander the legitimacy of contracts signed by the government of Kurdistan and the foreign companies."

A Sunni Arab lawmaker on Monday denounced laws barring former Saddam supporters from government jobs, saying they amount to "racism" and are aimed at punishing members of the minority Islamic sect.

Mutlaq al-Jubouri, a former deputy prime minister, said the committee to purge government institutions of high-level members of Saddam's ruling Baath Party was established only to punish the Sunni sect.

"This committee was founded not to uproot the Baath Party, but rather to uproot a section of the Iraqi people," al-Jubouri said.

But in a hopeful sign for political progress, lawmakers from Iraq's largest Sunni Arab bloc on Monday ended their boycott of parliament over the "house arrest" of their leader, Adnan al-Dulaimi, who also attended the session.

Al-Dulaimi, one of Iraq's most powerful Sunni Arab politicians, was kept at home for more than two days after one of his guards was allegedly discovered last week with the keys to a car laden with explosives near his office in Baghdad. Al-Dulaimi's son and 30 other people were arrested.

The government has said al-Dulaimi was prevented from leaving him home for his own safety. Defusing the crisis, the government moved him Sunday to a hotel in the heavily guarded Green Zone.