U.S. Marines landed Saturday in northern Iraq and began building the first center for Kurdish refugees on Iraqi territory, a U.S. Embassy official said.

Lt. Col. Mike Boyce said 400 Marines from the 24th Marine Expeditionary battalion flew about six miles from the Turkish border town of Silopi to Zakho, Iraq, and erected the tents.There were no problems and no sightings of Iraqi troops, said Boyce, the naval attache to the U.S. Embassy in Turkey. There was no indication when the first refugees could arrive.

Thousands of refugees have died in camps in Turkey and Iran or in the rugged mountains. Officials estimate 800,000 of Iraq's 4 million Kurds fled to the Turkish border, and 1.5 million are thought to have sought refuge along the border with Iran.

Army Lt. Gen. John M. Shalikashvili, who met Friday with Iraqi generals and warned them not to disrupt the relief effort, said security units will protect the teams building the camps.

"It was our intention to deploy the necessary security forces from the beginning to protect the humanitarian effort, and it is still our intention," he said.

Efforts to persaude the Kurds to return may include bringing Kurdish clan leaders to the camps or showing them video footage, a military official said.

But many Kurds say they are afraid to return as long as Saddam remains in power in Iraq.

U.S. officials continued to stress that their jurisdiction over the camps would be temporary. Shalikashvili said he would want to turn over responsibility of the camps "as rapidly and at the same time as prudently as possible" to the United Nations or other civilian organizations.

Asked whether he feared a renewed outbreak of fighting between Iraqi forces and the Kurdish rebels in or near U.S.-protected camps, Shalikashvili said: "I would be foolish to tell you that I am not concerned about it, but I must also tell you that my task is for this humanitarian effort to proceed."