Marines conducting two offensives in western Iraq on Saturday said they had killed at least 50 insurgents and freed four Iraqi captives near the Syrian border and launched a hunt for underground weapons caches along the shores of Tharthar Lake north of Baghdad.

Each of the operations involved a force of about 1,000 Marines and more than 100 Iraqi soldiers.

The heaviest fighting was in Karabilah, a desert outpost of low-slung buildings where Marines said insurgents had taken refuge after a U.S.-led assault in early May.

Marines have launched four offensives since early May in restive Anbar province, which military officials have described as a haven for foreign fighters entering Iraq from Syria. Most of the region's residents are Sunni Muslim Arabs, who are believed to make up the bulk of Iraq's insurgency.

Marine aircraft bombarded Karabilah on June 11 and returned to the town when intelligence showed a strong insurgent presence, said Col. Bob Chase, operations chief for the 2nd Marine Division. The current offensive, dubbed Operation Spear, began with airstrikes and light ground clashes Friday.

Marines approached Karabilah from the south and blocked off major routes leaving the city. After a firefight Saturday morning, they raided a house and found four Iraqi men blindfolded, shackled and badly bruised in a room concealed by curtains.

Marines also found photographs of Iraqi soldiers -- at least one of whom had been recently killed -- and DVDs showing a beheading and people being beaten, according to Chase.

"This appeared to be a very bad place" and it "shocked the Marines who found it," he said. "This was a significant find."

The rescued men, all of whom appeared to be in their twenties and thirties, had welts and bruises on their faces and backs and were taken to a medical facility for treatment, Chase said. In interviews, the men indicated they did not know why they had been taken captive and said their kidnappers had not interrogated them, Chase added.

Elsewhere in the town, Marines discovered munitions and parts for roadside bombs and car bombs stockpiled at a school, Capt. Jeffrey S. Pool, a Marine spokesman said. Instructions for assembling explosives were written on a blackboard.

Also, six civilians were wounded when insurgents stormed a building that was home to a family of nine and began firing at a U.S. and Iraqi patrol, Pool said.

U.S. and Iraqi troops suffered what Chase would specify only as "light casualties." He said the number of insurgents killed could be as high as 100 but that the total was difficult to determine because some were believed to have been inside buildings destroyed by F-18 fighter jets and support aircraft. Wire services reported that three Marines had been wounded since the operation began.

Chase also said no insurgents had been captured in Karabilah

Insurgents disputed the U.S. forces' account of their death toll. "That is a lie and not accurate," said Abu Aswad, a leader in the group al Qaeda in Iraq, run by the Jordanian extremist Abu Musab Zarqawi. "Only 13, including seven [foreign fighters], were killed."

The assault near Tharthar Lake began Saturday morning near the site of a vast underground bunker complex and about 50 weapons caches discovered by Marines this month. Dubbed Operation Dagger, it was centered on a string of small communities 50 miles northwest of Baghdad.

Few details were available Saturday evening, but Marines found one weapons stockpile and took two detainees after a series of minor clashes, including a roadside bomb attack, Chase said.

Elsewhere in Iraq on Saturday, two U.S. soldiers, a detainee traveling in their convoy and an Iraqi civilian were killed during a firefight with insurgents in the town of Buhriz, about 35 miles north of Baghdad, the military said in a statement. Five Iraqi police were wounded in the incident.

In Baghdad, Jawad Kadhem, a correspondent for the al-Arabiya television network, was shot in the neck and seriously wounded as he left a restaurant, the station reported. Also in the capital, a suicide bomber targeting an Iraqi military convoy killed two soldiers and wounded six, wire services reported, citing a police source.

And police in the city of Emkashifa discovered the bodies of two people who had been bound, tortured and shot with three bullets each, said Saad Muhammed Khudhayer, a doctor at Tikrit's General Hospital.

A Marine searches an Iraqi during Operation Dagger, one of two Marine offensives in the restive western province of Anbar launched since Friday.