BAGHDAD, Iraq - Four people have been detained in the killing of American Nicholas Berg, whose decapitation was captured on videotape, an Iraqi security official and a U.S. military official said today. The Iraqi official said the group that killed Berg was led by a relative of Saddam Hussein.

The suspects were former members of Saddam Hussein's Fedayeen paramilitary organization, the Iraqi security official said on condition of anonymity. Iraqi police arrested them on May 14 in a house in Salaheddin province, north of Baghdad. The province includes Tikrit, Saddam's hometown.

Speaking on condition of anonymity, a U.S. military official in Baghdad confirmed four people were in custody. The official did not say who was holding the suspects.

Another Iraqi official confirmed there were arrests in the Berg case, but would not comment further. The official also declined to be named.

The group that was involved in the killing of Berg was led by Yasser al-Sabawi, a nephew of Saddam Hussein, the Iraqi security official said. He said American intelligence had asked Iraqi authorities to hand over the suspects, but they were still in Iraqi hands.

Al-Sabawi was not among those arrested, the Iraqi official said.

Police intelligence agents arrested the suspects as they arrived to "plot other major operations," the official said without elaborating. Four suspects had arrived early for the 7 p.m. meeting and were inside the house, waiting for a fifth associate who escaped arrest, he said.

Police seized weapons and explosives at the site. The Iraqi official said the informant who tipped off authorities was killed by unidentified gunmen the day after the arrests.

American officials have said they believe Abu Musab al-Zarqawi, a Jordanian wanted for allegedly organizing attacks on U.S. troops in Iraq on behalf of al-Qaida, personally carried out Berg's killing.

The body of Berg, 26, was found May 8 near a highway overpass in Baghdad. He was last seen on April 10 when he left his Baghdad hotel.

A video posted May 11 on an al-Qaeda-linked Web site showed a bound Berg in an orange jumpsuit. He was sitting in front of five men, their faces masked, as one read an anti-American text.

After pushing Berg to the floor, the men severed his head with a knife and held it up for the camera. They said his killing was in response to the abuse of Iraqis at Abu Ghraib prison.