The suspected mastermind of beheadings and bombings threatened to assassinate Iraq's prime minister a week before the new government takes power. Insurgents launched simultaneous attacks on police stations in the western Iraqi city of Ramadi (search), killing 18 people and wounding 13, officials said.

The attacks across the so-called Sunni Triangle Thursday came a day after U.S. officials said that an airstrike killed 20 followers of the Al Qaeda (search)-linked militant, Jordanian-born militant Abu Musab al-Zarqawi (search). There was no immediate indication they were connected.

The attacks began at dawn in the western Iraqi cities of Ramadi (search) and Baqouba (search). Explosions also rocked the eastern side of the restive city of Sunni-Muslim city of Fallujah, witnesses said.

"We were inside the al-Qataneh police station and suddenly a very heavy explosion happened," 1st Lt. Ahmed Sami said from the insurgent stronghold of Ramadi, 60 miles west of Baghdad.

Another group attacked the Farook police station, also with rocket propelled grenades. In a third assault, insurgents attacked a Ramadi government building, destroying several police cars.

Clashes were also reported between police and insurgents in Baqouba, 35 miles northeast of Baghdad, according to police officials in the city.

Militants focused their anger on Prime Minister Iyad Allawi (search) and his government — the latest sign that the campaign of insurgent violence against the U.S. occupation is unlikely to end with the June 30 handover of power.

Allawi brushed off the threats, saying al-Zarqawi was "just a criminal who must be captured and tried."

The threat against his life came in an audiotape purportedly made by al-Zarqawi, found Wednesday on an Islamic Web site. The message also denounced Allawi's government as a tool of the "infidel foreigner."

Al-Zarqawi's group claimed responsibility for the beheading of American hostage Nicholas Berg last month and Kim Sun-il, a South Korean whose decapitated body was found Tuesday.

Hours after Kim's body was found, the U.S. military launched its second attack against al-Zarqawi in three days, with an airstrike on a suspected hideout in Fallujah late Tuesday.

A coalition military official said 20 foreign fighters and terrorists were believed to have been killed in the strike against a house used by al-Zarqawi's group.

Fallujah residents said the strike hit a parking lot, killing three people and wounding nine, according to hospital officials.

The al-Zarqawi recording warned Allawi that he had already survived "traps that we made for you" but vowed that the group would continue planning his assassination "until we make you drink from the same glass as Izzadine Saleem," the Governing Council president killed by a car bomb last month.

There was no way to authenticate the recording, but the voice sounded like al-Zarqawi, whose Tawhid and Jihad movement has been blamed for many of the bombings and assassinations that have killed hundreds of people, most of them Iraqis, in recent months.

The CIA was reviewing the tape.

In an interview with the Italian newspaper Il Giornale, Allawi dismissed al-Zarqawi as a criminal who would be caught and punished.

"Abu Musab al-Zarqawi doesn't threaten just me, but the entire country," Allawi told the newspaper, which released a copy of the interview Wednesday night.

"He has killed hundreds of Iraqis, has sown disorder and fear," Allawi was quoted as saying. "We are used to threats and we know how to deal with them and how to win."

In an interview Wednesday with Associated Press Television News, U.S. Brig Gen. Mark Kimmitt said many of the major attacks in Iraq are carried out by al-Zarqawi's forces, while former regime supporters are responsible for smaller assaults.

"He is a very, very crafty leader of a large network that is conducting terrorist operations inside this country," Kimmitt said. "The people of Iraq must understand they have a responsibility. They bear a responsibility to making sure we take Zarqawi and his network off of the street."

Al-Zarqawi's group killed Kim, a 33-year-old South Korean, after the Seoul government rejected its demands to withdraw troops from Iraq. His body was dumped on a road between Baghdad and Fallujah, a hotbed of Islamic extremism.

Iraq's interim president, Ghazi al-Yawer, said Kim's killing violated Iraqi and Islamic tradition and "completely tarnishes Iraq.

"How could we rebuild our country if we can't guarantee the safety of people who come to help build our country," al-Yawer said on the U.S.-funded TV station Al-Iraqiya.

Allawi told reporters Sunday that his government was considering martial rule in certain areas to restore order.

A group of masked militants claiming to represent resistance groups in Iraq warned against that step in a video aired Wednesday night on Al-Arabiya television.

They said they would "strike with God's might" if Allawi imposed emergency rule on behalf of the "occupation masters."

U.S. and Iraqi officials are bracing for stepped up violence ahead of the June 30 transfer of sovereignty, which marks the formal end of the U.S.-led occupation.

Nevertheless, U.S. and Iraqi officials say the handover schedule is on track. On Thursday, a ceremony is planned to mark the official transfer of the final 11 ministries to Iraqi control — including the defense, interior, justice and electricity ministries. Iraqis have already taken over the running of the other 15 ministries.

The military said insurgents staged at least six attacks on American convoys throughout Iraq on Wednesday, wounding one U.S. soldier and a civilian contractor.

Late Wednesday, insurgents hurled a hand grenade at the newly refurbished Iraqi Transportation Ministry, then engaged in a 10-minute gunbattle with security guards, injuring at least one, residents said.

Elsewhere, a roadside bomb in Baghdad killed a policeman, a woman and her child, Iraqi police said.

Another roadside bomb in the northern city of Mosul killed one Iraqi soldier and wounded four others. In Ramadi, an insurgent stronghold 60 miles west of Baghdad, gunmen killed two policemen and wounded a third in a drive-by shooting, witnesses said.

In other developments:

— NATO was considering an Iraqi request for training and other technical assistance for security forces to combat militants, but not troops. The United States has been lobbying for a NATO role in Iraq, despite resistance from key members such as France and Germany.

— Iraqi engineers said they had resumed pumping crude oil through a pipeline between northern Iraq and Turkey that was attacked last month. Officials with the State Oil Marketing Organization said they were unaware the pipeline was back up.

— Top followers of radical Shiite cleric Muqtada al-Sadr rejected an invitation to join a national conference that will select a council to advise Iraq's interim government.