OBEIDI, Iraq -- The U.S. military declared Saturday that its weeklong offensive near the Syrian border had "neutralized" an insurgent sanctuary there. But less than 24 hours earlier, fighters armed with machine guns and rocket-propelled grenades swaggered through the desert town where the campaign began.

U.S. forces killed more than 125 insurgents, injured many more and detained 39 "of intelligence value" during the campaign aimed at followers of Iraq's most wanted terrorist, Abu Musab al-Zarqawi, the military said in a statement.

Nine U.S. Marines were killed and 40 injured during the offensive known as Operation Matador -- one of the largest American campaigns since militants were driven from Fallujah six months ago. The number of civilian casualties was not immediately known.

American troops, backed by warplanes and helicopter gunships, swept through desert outposts along ancient smuggling routes, believed to be staging areas for foreign fighters who slip over the border and collect weapons to launch deadly attacks in Iraq's major cities.

Numerous weapons caches with machine guns, mortar rounds and rockets were discovered. Six car bombs and material for making other improvised explosive devises were also found, the statement said.

The military said the operation confirmed its intelligence about a region north of the Euphrates River, including the existence of "cave complexes" used by insurgents in the nearby escarpment. It did not elaborate.

"Regimental Combat Team-2 started and ended this operation as planned, accomplished its mission and secured all objectives," Maj. Gen. Richard Huck said in the statement. "Coalition and Iraqi security forces will return again to this area in the future."

Defiant opposition

But in Qaim, the town where the campaign began, masked fighters remained in plain sight Friday, setting up checkpoints and vowing to defend the town if U.S. forces return.

The U.S. assault came amid a surge of militant attacks that have killed more than 450 people in just over two weeks since Iraq's first democratically elected government was announced.

At least 13 more Iraqis died Saturday in a series of ambushes and bombings. They included a senior Iraqi Foreign Ministry official slain in a drive-by shooting outside his Baghdad home Saturday night, police said. Three bystanders were also injured in the attack that killed Jassim Mohammed Ghani, a director general in the ministry, police Capt. Talib Thamer said.

The U.S. offensive began May 7 in Qaim, a town 200 miles northwest of Baghdad on the southern bank of the Euphrates River. American intelligence indicated insurgents had massed north of the waterway, according to reporters embedded with the assault. But as soldiers built a pontoon bridge, they started taking mortar fire from nearby Obeidi.

When U.S. forces entered the village May 8, they confronted well-equipped fighters -- some with body armor -- fighting from rooftops, basements and sandbag bunkers positioned in front of some homes. U.S. forces pounded the area with air strikes and artillery barrages and some 70 insurgents were killed in the first 24 hours of the operation alone.

Pentagon officials conceded, however, that the insurgents were better trained and equipped than previously thought.

The next day, U.S. forces crossed the Euphrates and pushed along the winding river to the border, meeting little resistance, the military said.

Periodic airstrikes continued into Friday, including one that killed 12 insurgents manning a checkpoint east of Husaybah, a nearby village, the military said. Another Friday air strike targeted a suspected terrorist safe house in nearby Karabilah. Secondary explosions indicated the presence of weapons and munitions in the building, the military said.

But insurgents also inflicted a toll, reportedly killing six Marines in one squad when their troop transporter hit a bomb near Karabilah on Wednesday.

A long column of U.S. troops, backed by tanks and helicopters, rolled back across the river Saturday and surrounded Obeidi, sending frightened villagers scurrying into their homes.

Shelling began several hours later, damaging a house in the old part of the village and wounding five people, said Dr. Saadallah Anad at Obeidi General Hospital. Anad said he did not know if it was hit by U.S. weapons fire.

U.S. military spokesman Capt. Jeffrey Pool said Marines conducted a "cordon and search" operation in the area, looking for insurgents, foreign fighters, weapons and bomb-making material. But he said Obeidi was not hit by air or artillery strikes on Saturday.

Rival groups of insurgents also were fighting among themselves around Qaim, trading mortar, rocket and machine gun fire almost nightly, Pool said. Residents acknowledged fighting in Qaim and surrounding villages began before the U.S. offensive, characterizing it as tribal clashes.

Residents reached by telephone in the old part of Obeidi said U.S. vehicles rolled through their area but met no resistance and withdrew late Saturday.

Thousands fled the area during the offensive, pitching flimsy tents along sand-blown desert highways or seeking shelter in schools and mosques in nearby towns.

The military denied resident reports that they had been without water and electricity in some areas since the offensive began.

"Throughout the course of the operation, Marines strove to ensure the well-being of the local Iraqi citizens," the statement said. "According to commanders in the area, the Marines were greeted with greater hospitality from local villagers than is normally encountered."

Elsewhere Saturday, U.S. airstrikes destroyed two unoccupied buildings near Fallujah that the military identified as an insurgent command center, weapons storage site, detention and possible torture facility. It was not immediately clear if there were any casualties in the attack, about 40 miles west of the Iraqi capital.

Meanwhile, arrest warrants were issued against two former Cabinet ministers as the new government cracks down on corruption, according to officials in the office of Prime Minister Ibrahim al-Jaafari and his party.

Former Transport Minister Louei Hatim Sultan al-Aris was charged with "administrative corruption," while ex-Labor Minister Leila Abdul-Latif was accused of "financial corruption" and bringing back into the government members of Saddam Hussein's brutal regime, said Jawad al-Maliki, a senior member of al-Jaafari's Dawa Party.

Al-Aris's whereabouts are unknown, but Abdul-Latif remains in the country, he said.

A 30-year-old detainee detained as a "security threat" at southeastern Iraq's Camp Bucca prison died of a heart attack Saturday, the U.S. military said. An investigation is underway into his death, the military said. Camp Bucca holds more than 6,000 Iraqi detainees.