U.N. weapons experts interviewed two Iraqi scientists in their homes Thursday, conducting their first surprise inspections of private residences.

Thursday's house searches and a visit a day before to a presidential palace suggested the inspectors are using new intelligence in their search for nuclear, chemical and biological weapons and programs to develop them.

The inspectors — along with Iraqi escorts and journalists — arrived in al-Ghazalia, a west Baghdad residential district, shortly before 9 a.m. Thursday and cordoned off a street by parking their vehicles across the road at both ends.

The inspectors, as is usually the case, did not speak to reporters. An Iraqi official on the scene said they entered the homes of Faleh Hassan, a physicist, and Shaker el-Jibouri, another nuclear scientist, who live next door to one another.

Neither man was at home when the inspectors arrived and one of the homes was occupied by women alone, neighbors said. Arab social convention prohibits strangers from entering a private home when there are no men present, and the inspectors waited up to an hour for the men to return before entering, neighbors and other witnesses said.

Inspectors also searched a shack on a nearby lot.

They left the scientists' houses after about three hours, but a few remained in the neighborhood. Reporters could not see if the inspectors removed any material from the homes. It also was unclear if they were able to speak to Hassan and el-Jibouri in private, away from Iraqis whose official assignment is to help smooth the way for the inspectors, but who likely also act as their government's eyes and ears.

Iraq in late December handed over to the inspectors a list of its scientists. In addition, U.N. officials have said they are receiving intelligence from the United States, which claims to have proof Iraq is hiding information about banned weapons.

Chief U.N. inspector Hans Blix and Mohamed ElBaradei, chief of the U.N. nuclear agency, will visit Baghdad on Sunday and Monday to press Iraqi officials for more information.

ElBaradei, speaking to reporters in Moscow Thursday, said the inspectors' work was inching forward but that the team needed more from Iraq, including interviews with scientists and documents that would make it possible to determine whether any past weapons programs had been discontinued.

As he left U.N. headquarters for Europe en route to Baghdad, Blix said Wednesday he will tell Iraq the situation is "very dangerous" but it can still prevent war by providing new evidence about its weapons programs.

Iraq got similar advice from Egyptian President Hosni Mubarak, who urged it "to complete what the inspectors described as gaps in the report" that Baghdad delivered to the United Nations.

"The current crisis has put all the countries of the region in a state of uneasiness," Mubarak was quoted as telling top Egyptian editors who accompanied him earlier this week on a trip to Saudi Arabia to discuss the Iraq crisis.

A day earlier, inspectors infuriated President Saddam Hussein's government with a visit to one of his presidential palace compounds, where they spent four hours searching two office complexes and opening safes. Iraq has long resented searches in Saddam's palaces — of which there are dozens — calling them offenses to its sovereignty.

Iraq's Foreign Ministry called Wednesday's palace inspection visit a "clearly provocative step to harass important national security sites" and said the inspection had "no relation at all to so-called disarmament."

Dimitri Perricos, who led the palace inspection team, told reporters Wednesday the two office complexes in the presidential compound attracted the inspectors' interest because satellite images showed they had high walls and a double fence.

In the past, Iraqi officials resisted palace searches. But the current inspection regime, backed by a stringent U.N. Security Council resolution, allows surprise inspections of any site.

The inspectors have been accused of being spies by Saddam and his aides. Resentment of the inspectors was likely to be compounded by Thursday's house searches.

The inspectors are charged with verifying Iraq's claims that it has eliminated all its nuclear, biological and chemical weapons, as well as long-range missiles.

The United States and Britain insist Iraq retains such weapons and have threatened military action unless its government cooperates fully with the inspectors. Amid an increasing U.S. military buildup in the Gulf, President Bush said Tuesday that "time is running out" for Saddam to disarm.

Also Thursday, a second team of inspectors visited a site belonging to an Iranian dissident group, the Mujahedeen Khalq, just west of Baghdad in an area called Abu Ghraib.

It was their second search of a Mujahedeen Khalq site in two days. The group seeks the violent overthrow of the Iranian government and has military bases in eastern Iraq along the Iranian border. It often claims responsibility for rocket and mortar attacks inside Iran. The United States regards the group as a terrorist organization.