In the deadliest reported firefights in Iraq since the fall of Saddam Hussein's regime, U.S. forces killed at least 54 Iraqis and captured eight others while fending off simultaneous convoy ambushes Sunday in the northern city of Samarra.

At least five U.S. soldiers, 18 Iraqi attackers and a civilian were injured.

Just minutes later, two South Korean contractors were killed nearby in a third ambush, part of what U.S. officials called a new campaign aimed at undermining international support for the occupation.

Attacks on Saturday had killed seven Spaniards, two Japanese diplomats and a Colombian oil worker.

Tanks and cannons were used to fight off the ambushes on the two convoys, which were delivering new Iraqi currency to banks and were being escorted by a U.S. military unit of 100, with M1A1 tanks (search) and Bradley armored vehicles (search).

"It was a well-organized and complex ambush, but they obviously picked the wrong convoy to attack. They could not have known," a U.S. military source told Fox News.

Capt. Andy Deponai, whose company took part in the fighting, said the guerrillas had deployed about 30-40 men at each ambush site.

Sources told Fox News that the 54 people killed in the battle included 46 Iraqi fighters and eight Iraqi civilians.

Local residents said Monday the Iraqi casualty figure was much lower than what the U.S. reported and that the dead were mostly civilians.

West of Baghdad, assailants ambushed another U.S. military convoy with small-arms fire on Monday, killing one soldier, the U.S. military said. The attack occurred near Habbaniyah (search), 50 miles west of the Iraqi capital, the military said. The soldier's name was withheld pending notification of next of kin.

The U.S. military said the Samarra attackers, many wearing uniforms of Saddam's Fedayeen paramilitary force, struck at the U.S. convoys at opposite sides of Samarra, 60 miles north of Baghdad.

The scars of the battle were evident. About a dozen cars lay destroyed in the streets, many apparently crushed by tanks, and bullet holes pocked many buildings. A rowdy crowd gathered at one spot, chanting pro-Saddam slogans. One man fired warning shots in the air when journalists arrived at the scene.

There was no U.S. military presence in the city center on Monday. Shops opened, and residents moved around town.

At a news conference at a U.S. military base in Samarra, Col. Frederick Rudesheim said the American convoys were on a mission to deliver currency to banks when the coordinated ambushes took place.

"That was a given location that they knew we would go to," Rudesheim said. "This was done in a concerted fashion."

At the U.S. base, half a dozen suspects were seen with bags over their heads and their hands bound by plastic cuffs.

After barricading a road, the attackers opened fire from rooftops and alleyways with bombs, small arms, mortars and rocket-propelled grenades, said Lt. Col. William MacDonald of the 4th Infantry Division. U.S. troops responded with rifles, 120mm tank rounds and 25mm cannon fire from Bradley fighting vehicles.

"It sounds like the attack had some coordination to it, but the soldiers responded, used their firepower, used tank and Bradley fire and other weapons available to them, to stop this attack and take the fight to the enemy," he said, adding that U.S. fire destroyed three buildings the attackers were using.

Many residents said Saddam loyalists attacked the Americans, but that when U.S. forces began firing at random, many civilians got their guns and joined the fight. Many said residents were bitter about recent U.S. raids in the night.

"Why do they arrest people when they're in their homes?" asked Athir Abdul Salam, a 19-year-old student. "They come at night to arrest people. So what do they expect those people to do?"

"Civilians shot back at the Americans," said 30-year-old Ali Hassan, who was wounded by shrapnel in the battle. "They claim we are terrorists. So OK, we are terrorists. What do they expect when they drive among us?"

Many residents said the Americans opened fire at random when they came under attack, and targeted civilian installations. Six destroyed vehicles sat in front of the hospital, where witnesses said U.S. tanks shelled people dropping off the injured. A kindergarten was damaged, apparently by tank shells. No children were hurt.

"Luckily we evacuated the children five minutes before we came under attack," said Ibrahim Jassim, a 40-year-old guard at the kindergarten. "Why did they attack randomly? Why did they shoot a kindergarten with tank shells?"

"We have been very aggressive in our convoy operations to ensure the maximum force protection is with each convoy," MacDonald said. "But it does send a clear message that if you attempt to attack one of our convoys, we're going to use our firepower to stop that attack."

Military officials in Baghdad said they had not reported a deadlier attack since May 1, when President Bush declared major combat over. U.S. officials have only sporadically released figures on Iraqi casualties, and would not say whether there has been a deadlier firefight that went unreported.

The scale of the attack and the apparent coordination of the two operations showed that rebel units retain the ability to conduct synchronized operations despite a massive U.S. offensive this month aimed at crushing the insurgency.

MacDonald said the Sunday attack on the South Koreans on the highway between Samarra and Tikrit, which killed two and wounded two others, had no apparent link to the attacks on the U.S. convoys.

The South Koreans were electricians who were building power lines for the Seoul-based Omu Electric Co., said Lee Kwang-jae, director general of South Korea's Foreign Ministry.

In Seoul, President Roh Moo-hyun on Monday condemned the attack as "intolerable" terror, and his government said the attack would not affect plans to send up to 3,000 troops to Iraq.

The bodies of the two Japanese diplomats killed on Saturday were flown to Kuwait and arrangements are being made for transporting them home, a Japanese diplomat said Monday on condition of anonymity.

Japanese Prime Minister Junichiro Koizumi reiterated Monday his vow that the attack on the Japanese diplomats would not alter Tokyo's commitments to send non-combat troops, provide humanitarian aid and participate in the reconstruction of Iraq.

At least 104 coalition troops have died in Iraq in November, including 79 American troops. In terms of coalition losses, it has been the bloodiest month of the war that began March 20.

As of Wednesday, Nov. 26, 434 U.S. service members have died since the beginning of military operations in Iraq, according to the Department of Defense. Of those, 298 died as a result of hostile action and 136 died of non-hostile causes, the department said. This total did not include Monday's reported death.

Fox News' Steve Centanni and the Associated Press contributed to this report.