A suicide bomber detonated an explosive belt Saturday night inside a Shiite Muslim mosque in a town south of Baghdad, igniting cooking gas in a tanker parked outside and setting off a massive fireball that killed at least 54 people, wounded 82 and destroyed or damaged homes more than a half-mile away, police said.

The unidentified bomber struck at 8 p.m. in Musayyib, a town about 35 miles south of Baghdad in a largely lawless part of Babil province that has come to be known as the triangle of death. A spokesman for the provincial police, Capt. Muthanna Ahmed, said by telephone that the attacker detonated his belt inside the mosque and could not have known the fuel tanker had been parked nearby while its driver was eating dinner at a local restaurant. As a result, Ahmed said, the apparent attempt at killing a relatively small group of worshipers resulted in a conflagration that was "just like a nuclear bomb explosion."

The attack, a rare act of violence inside a mosque, appeared to be the deadliest in Iraq since Feb. 28, when a suicide bomb in nearby Hilla killed 125 people, most of them police and military recruits.

Ahmed said many of the wounded were critically burned and that Musayyib's medical facilities could not handle the huge number of casualties. Some of the wounded were taken to clinics in Hilla and Karbala, while provincial officials appealed for medical workers in the area to go to Musayyib as quickly as possible.

Firefighters already were converging on the town to battle blazes that were still raging late into the night, said Ahmed, who estimated that the devastation extended from the mosque for about 1,100 yards in every direction.

The victims were among at least 76 people killed in attacks across the country.

Meanwhile, the U.S. military announced in a statement that 11 American soldiers had been charged with violating military regulations in connection with alleged assaults on suspected insurgents. The statement gave no details about the soldiers' violations except to note that none of the suspected insurgents needed medical treatment and only one of them is currently in U.S. custody.

"All Task Force Baghdad soldiers are expected to act appropriately and to treat all persons under their control with dignity and respect. Allegations of illegal activities will always be thoroughly investigated," said Lt. Col. Clifford Kent, a spokesman for the task force, which is responsible for security in and around the capital. "The unit involved has been pulled off-line to complete the inquiry and retraining."

The new investigation is the latest of several cases in which U.S. service personnel have been charged with abuse in Iraq. Last year, in the most notorious case, photographs of Iraqi detainees subjected to sexual humiliation in Baghdad's Abu Ghraib prison led to the conviction of one soldier in a court-martial. Four others pleaded guilty to charges arising from the case.

Early Saturday morning, in Iskandariyah, a volatile town about 15 miles north of Musayyib, 10 people were killed, including four Iraqi soldiers, and up to 20 wounded by a suicide car bomb. The attack occurred at 1 a.m., while Iraqi soldiers were manning a checkpoint and searching cars for suspected insurgents, Ahmed said.

Musayyib and surrounding towns have been wracked by violence for months. The area has been terrorized by insurgents who rob or kill travelers at illegal checkpoints along local roads. A large proportion of travelers in the area are Shiites heading south from Baghdad to the Shiite holy cities of Karbala and Najaf, while the insurgents are overwhelmingly Sunni.

The sectarian divide between Iraq's long-repressed Shiite majority and the Sunni minority that ruled the country for decades has been a principal causeof the violence that has surged since late April, when modern Iraq's first Shiite-led government took office. Car bombings in Shiite neighborhoods of Baghdad, unexplained killings of groups of Sunni men in and around the capital and assassinations of clerics from both branches of Islam have accounted for much of the bloodletting, which has killed more than 1,500 Iraqis since April 28.

In Najaf, the office of Iraq's preeminent Shiite cleric, Grand Ayatollah Ali Sistani, issued a statement late Saturday night condemning the violence. "This is a tragedy for the people -- Shiite and Sunni," said the statement, which contended that insurgents had come to the area from cities in the north "to kill the innocent." Sistani called on all Iraqis to control themselves and allow their passions to cool, the statement said.

In the southern city of Amarah, an apparent roadside bomb killed three British soldiers and wounded two, according to a British Defense Ministry statement quoted by news agencies. Such attacks are rare in the relatively quiet southern provinces of Iraq where Britain has security duties. A total of 92 British soldiers have died in Iraq since the U.S.-led invasion in 2003, including 53 killed in combat.

Six policemen were killed and 20 wounded in a suicide attack near Mosul, 220 miles north of Baghdad. The attack took place in the town of Hammam Alil, six miles south of the city, where a man in police uniform entered the town's police station and detonated a belt of explosives he wore, said Mosul police's press officer, Maj. Ahmed Lazim.

And in Baghdad, three policemen were killed and 20 wounded by a car bomb that targeted a police patrol in the Doura neighborhood, the Reuters news agency reported.

U.S. and Iraqi officials have repeatedly said insurgent attacks in Baghdad have decreased since a security operation was launched in late May. The operation, officially dubbed Operation Lightning and said to be the biggest Iraqi operation since the invasion, resulted in the killing or arrests of hundreds of alleged insurgents, according to officials. In the past week, however, the capital has been hit by repeated suicide bombings, including at least seven on Friday.

Special correspondents Saad Sarhan in Najaf, Omar Fekeiki in Baghdad and Dlovan Brwari in Mosul contributed to this report.