A car bomb obliterated a tent packed with mourners at the funeral of a Kurdish official in northern Iraq (search) on Sunday, killing 25 people and wounding more than 50 in the single deadliest attack since insurgents started bearing down on Iraq's newly named government late last week.

The blast capped four exceedingly violent days in which at least 116 people, including 11 Americans, were killed in a storm of bombings and ambushes blamed on Iraqi insurgents, believed largely populated by members of the disaffected Sunni Arab (search) minority.

The Sunnis were dominant for decades under Saddam Hussein but were mainly shut out of the new government announced Thursday. The skyrocketing violence since then is viewed by some as a response to political developments that the United States (search) and the Shiite-dominated power structure had hoped would tamp down the bloodshed.

Despite the unrelenting violence, Iraq's national security adviser said Sunday the fledgling government was making progress against the insurgents.

"There is no shadow of doubt in my mind that by the end of the year, we would have achieved a lot," Mouwafak al-Rubaie said in a televised interview. "Probably the back of the insurgency has already been broken."

Iraqi militants also released a video purporting to show Iraq's latest foreign hostage — an Australian married to an American and living in the San Francisco area. Douglas Wood, 63, was shown seated between two masked militants pointing automatic weapons at him. His wife, Pearl, told The Associated Press she saw the tape and the man being held was definitely her husband. She said he had been in Iraq about 18 months, working as an engineer.

The car bomb attack occurred in Tal Afar, 93 miles east of the Syrian border, the U.S. military and a provincial official said. Mourners had gathered for the funeral of Sayed Talib Sayed Wahab, an official of the Kurdish Democratic Party, said deputy provincial governor and party spokesman Khisru Goran, speaking from nearby Mosul.

Goran said a car plowed into the funeral tent and exploded, but the U.S. military said it was not a homicide attack. About 25 people were killed and more than 50 wounded, the U.S. military said.

U.S. troops, Iraqi police and ambulances raced to the carnage, but unidentified gunmen blocked the road and fighting broke out, Goran said.

At least six other car bombs — one of them a homicide attack — and five roadside explosions hit Baghdad on Sunday, killing six Iraqis, wounding more than 20 civilians, six Iraqi police officers and five U.S. soldiers.

In one blast, the attacker failed to fully detonate the explosives inside his car outside an American base in Baghdad, the military said in a statement. U.S. soldiers pulled the driver out of his burning car, and the man later said he was forced to carry out the attack to protect kidnapped family members, according to the statement.

Five more explosions rocked the capital late Sunday. Two roadside bombs detonated near a small amusement park in central Baghdad, killing one Iraqi and wounding two others, while two more roadside bombs targeting police patrols in western Baghdad wounded six officers, they said.

Police had no immediate information on the fifth blast.

Insurgents also ambushed an Iraqi checkpoint on a small road near Diala Bridge in eastern Baghdad, killing five policemen and injuring one, police said. Insurgents in a pickup truck started firing machine guns and rocket-propelled grenades early Sunday, police said. Other insurgents appeared from behind nearby trees and joined the attack.

Six more policemen and two civilians were injured when gunmen fired on two separate patrols, police said.

U.S. and Iraqi officials had hoped to dent support for the militants by including members of the Sunni Arab minority in a new Shiite-dominated Cabinet that will be sworn in Tuesday. However, the lineup named by incoming Prime Minister Ibrahim al-Jaafari after months of political wrangling excluded Sunnis from meaningful positions and left the key defense and oil ministries — among other unfilled posts — in temporary hands.

Since the late summer of 2003 and just a few months after U.S.-led forces toppled Saddam, insurgents have used spectacular attacks and hostage takings to drive home their opposition to U.S.-led forces and their Iraqi allies.

In the videotape announcing Wood's capture, he appealed to President Bush, Australian Prime Minister John Howard and Californian Gov. Arnold Schwarzenegger to order coalition forces out of Iraq and to let Iraqis look after themselves, saying he did not want to die.

"My captors are fiercely patriotic. They believe in a strong united Iraq looking after its own destiny," Wood said on the tape.

A militant group calling itself the Shura Council of the Mujahedeen of Iraq claimed responsibility for the kidnapping. The group previously said it abducted a Turk, who was freed in September.

Australian Prime Minister John Howard said Monday he would not negotiate with Wood's captors. Within days, Australia will have more than 1,300 troops in Iraq.

"We can't have the foreign policy of this country dictated by terrorists," he told Australian Broadcasting Corp. radio.

More than 200 foreigners have been kidnapped in Iraq since Saddam's regime collapsed in April 2003. More than 30 hostages have been killed by the captors.

The British Foreign Office, meanwhile, announced three arrests in the abduction of a British aid worker believed slain last year, saying they were made after an early-morning sweep of an insurgent area 15 miles south of Baghdad.

An intelligence official with the Iraqi Interior Ministry said five Iraqi suspects were apprehended and confessed to a role in killing Margaret Hassan, the director of CARE International in Iraq. Martin Cronin, first secretary at the British Embassy in Baghdad, said he was not aware of any confessions.

U.S. and Iraqi forces also recovered items apparently related to Hassan, the British Embassy said in Baghdad. The items included a purse, a woman's clothing and CARE documents signed by Hassan, the Iraqi official said on condition of anonymity.

Hassan, 59, who also held Irish and Iraqi citizenship, was abducted in Baghdad on Oct. 19 on her way to work. Her captors later issued videos showing her pleading for British Prime Minister Tony Blair to withdraw troops from Iraq and calling for the release of female Iraqi prisoners.

On Nov. 16, the Arab satellite television station Al-Jazeera said it had received a video showing a hooded militant shooting a blindfolded woman in the head. British officials said they believed the woman in the video was Hassan, and her family said they believed she was dead, but no body was found.

Also Sunday, the Italian government said its report on the killing of an Italian intelligence agent by U.S. soldiers in Baghdad would show problems of coordination with authorities in Iraq and with rules of engagement for checkpoints.

The Foreign Ministry in Rome said the Italian report will be made public Monday, providing its own version of the March 4 "friendly fire" shooting death of agent Nicola Calipari, who had just won the release of an Italian hostage, journalist Giuliana Sgrena.

In its report on the incident released Saturday, the U.S. military cleared American soldiers in Calipari's death and recommended no disciplinary action. The Americans contend the car Calipari was riding in as he headed to Baghdad airport with the ex-hostage did not slow down at the checkpoint.

The two Italian experts who participated in the joint U.S.-Italian probe of the shooting refused to sign off on the Americans' conclusions.