Updated

Insurgents using homicide and roadside bombs killed at least 21 people, including a U.S. soldier, on Thursday in the latest of a series of attacks aimed at wrecking Iraq's constitutional referendum next week.

The attacks came as Iraqis began picking up copies of the draft constitution that they will vote on Oct. 15 after the country's Shiite-led parliament ended a bitter dispute with Sunni Arabs (search) about how the referendum will be conducted.

Under U.S. and U.N. pressure, parliament Wednesday reversed its last-minute electoral law changes, which would have ensured passage of the new constitution but which the United Nations (search) called unfair.

Sunni Arab leaders who had threatened a boycott because of the changes said they were satisfied with Wednesday's reversal and are now mobilizing to defeat the charter at the polls. But some warned they could still call a boycott to protest major U.S. offensives launched in the past week in western Iraq, the Sunni heartland.

Thursday's two deadliest attacks in Baghdad (search) involved homicide car bombers.

A man wearing an explosives belt got onto a minibus carrying 14 people — including students, workers and policemen heading to the police academy, and detonated his payload, said Police Capt. Abbas Ali. The bomber, who sat next to the driver, struck as the bus passed a police patrol at the intersection where the academy is located, about 400 yards from the Oil Ministry.

At least nine people were killed and nine others wounded, Ali said. The bus was left a burned-out husk.

Earlier, in Karrada, another part of eastern Baghdad, a homicide car bomb exploded near a convoy of private security contractors, killing three bystanders and wounding six others, police Maj. Mohammed Yunis said. One of the four white sport utility vehicles in the convoy was damaged, but none of the foreigners in them was hurt.

In northern Baghdad, a roadside bomb hit a U.S. Army patrol in northern Baghdad, killing one soldier, said military spokesman Sgt. 1st Class David Abrams.

That attack raised to 1,945 the number of U.S. military members who have died since the war began in 2003, according to an Associated Press count.

Four other U.S. soldiers were slightly wounded when a car bomb hit their patrol in central Baghdad, setting off fighting with small-arms fire and U.S. helicopters, Abrams said.

About 20 miles south of the capital, a roadside bomb hit a police patrol on a highway, killing five policemen and wounding two, said police Capt. Talib Thamir.

A shooting and a roadside bomb in the towns of Taji and Udaim, north of Baghdad, killed two Iraqi soldiers and a policeman.

At least 292 people have been killed by insurgents in Iraq in the past 11 days.

That includes Wednesday's bombing of a Shiite mosque in Hillah, a city south of Baghdad, killing 25 and wounding 93, as hundreds of worshippers gathered to pray at the start of the Islamic month of Ramadan and for the funeral of a man killed two days ago in a blast at his restaurant.

The insurgent attacks — often targeting Shiite Muslims — are aimed at wrecking the referendum. Al Qaeda in Iraq, which has declared "all-out war" on Shiites, has called for stepped-up violence during Ramadan.

Elsewhere, insurgents bombed a pipeline near the oil-rich northern city of Kirkuk, sending plumes of black smoke and fire up into the air. The pipeline connects oil fields with Kirkuk's refineries, said police Capt. Farhad Talabani. Iraq's Northern Oil Co. would soon repair the damage, as it has after many other attacks, he said.

Thousands of U.S. and Iraqi troops also were waging two major offensives in western Iraq, the Sunni heartland, in an attempt to put down Al Qaeda in Iraq insurgents ahead of the vote.

At least 42 insurgents have been killed in the "Iron Fist" offensive, which began Saturday near the Syrian border, and six in the "River Gate" offensive, which started further east Tuesday, the U.S. military said. Scores of suspected insurgents have been detained, and at least four American servicemen have died in the two offensives, the military said.

An 43-year-old detainee also died Wednesday of an apparent heart attack at U.S. Camp Bucca, the military said. About 12,300 Iraqi and foreign detainees are being held there and at other U.S. detention centers in Iraq, such as the notorious Abu Ghraib prison.

In London, British Prime Minister Tony Blair said new explosive devices used against coalition forces in Iraq "lead us either to Iranian elements or to Hezbollah."

While stressing that Britain "cannot be sure" about Iran's possible role, he linked the issue to the diplomatic confrontation over Iran's nuclear program.

"There is no justification for Iran or any other country interfering in Iraq," Blair said at a news conference with Iraqi President Jalal Talabani.

On Wednesday, Press Association reported that a senior government official said Britain believed Iran's Revolutionary Guard supplied explosives technology to insurgents in Iraq that was used to kill eight British soldiers over the summer.

Iran "categorically denied the strange accusation," the official Islamic Republic News Agency reported Thursday.

In Beirut, Hezbollah denounced Blair's accusations as "lies," saying it believes he made the accusation "to defend the inability of the occupation to face the growing resistance inside Iraq."

Iran's Revolutionary Guards are believed to have provided training, equipment and money to Hezbollah, treating it almost like an arm of the guard. In Lebanon, Hezbollah focuses on fighting against Israel, but the group also more broadly shares the Revolutionary Guard's anti-U.S. rhetoric and goal of promoting Islamic theocracy.

Tehran is estimated to provide Hezbollah with $10 million-$20 million monthly.