An Iraqi nuclear physicist left his home Thursday and went with U.N. weapons inspectors to a field outside Baghdad where they examined what seemed to be a man-made mound of dirt.

Following the visit to the field, the physicist, Faleh Hassan, was seen entering a Baghdad hotel where some inspectors are living, carrying the box the size of a small television set visibly stuffed with documents.

The dramatic developments began shortly before 9 a.m. Thursday when a convoy of vehicles carrying inspectors, Iraqi escorts and journalists arrived in al-Ghazalia, a residential district in western Baghdad.

The U.N. personnel cordoned off a street by parking their vehicles across the road at both ends.

An Iraqi official on the scene said the inspectors entered the homes of Hassan and Shaker el-Jibouri, another nuclear scientist, who lives next door. 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, and were seen going through documents at a table set up near Hassan's front door.

The visits were the first surprise inspections of private residences. Coupled with Wednesday's inspection of a presidential palace, the visits suggested the inspectors are using new intelligence in their search for nuclear, chemical and biological weapons.

After about six hours, the inspectors got into an animated discussion with Iraqi liaison officers, whose official assignment is to help smooth the way for the inspectors, but who likely also act as their government's eyes and ears.

"I'm not happy about all of this," Dimitri Perricos, a inspection team leader, could be heard telling Iraqi officials.

Perricos and Hassan then got into a car which led the convoy about 10 miles west of Baghdad, where it stopped at an agricultural area known as al-Salamiyat.

There, Hassan, two inspectors and a liaison officer walked across a footbridge over a canal to a bare field that contained what appeared to be a man-made earth mound.

The group spent about five minutes looking at the mound before returning to their vehicles and heading back to Baghdad. As usual, the inspectors had no comment for reporters and it was not clear what they were looking for.

Iraqi presidential adviser Amir al-Saadi later said Hassan had taken the inspectors to a farm he once owned but sold in 1996. Al-Saadi offered no other information on the site.

It was also not known what caused the heated discussion or angered Perricos. The inspectors have been demanding they be allowed to speak with scientists alone -- away from the Iraqi liaison officers whose official job is to help smooth the way for the inspectors, but who likely also act as the government's eyes and ears. The Iraqis, in turn, have complained that the inspectors are too intrusive.

After the visit, a visibly angry el-Jibouri told reporters the inspectors spent two hours in his home -- and cordoned it off for much longer -- looking into everything, "including beds and clothes."

"This is a provocative operation," el-Jibouri said. "They did not take away any documents but they looked at personal research papers."

Later in the day, al-Saadi said in a press conference that Iraq was ready to resolve any problems with U.N. inspectors over its weapons declaration.

"All is going well so far. There are some remarks here and there and there are some complaints here and there, but we expect to resolve those questions or complaints Sunday and the next day," he said.

Al-Saadi was referring to a visit by chief U.N. weapons inspector Hans Blix and Mohamed ElBaradei, chief of the U.N. nuclear agency, to Baghdad on January 19-20. Blix and ElBaradei said Thursday that Iraq must do more to prove it does not possess chemical, biological or nuclear weapons in order to avoid military conflict.

The United States and Britain insist Iraq retains weapons of mass destruction and long-range missiles 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.

Under the tough U.N. sanctions demanded for by the U.S. and passed by the Security Council in this past autumn, inspectors are allowed to speak to Iraqi scientists in private and even take them outside the country for interviews — requirements Washington hopes will prompt scientists to reveal hidden arms programs.

Inspectors have spoken with engineers and experts at sites they have searched and have reported two formal interviews with Iraqi scientists, both on nuclear programs. Both scientists who were formally interviewed told reporters they wanted to be interviewed with Iraqi officials in attendance and were.

Iraqi officials have said they do not believe it is necessary for scientists to be taken out of the country but will allow it if a scientist consents.

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.

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.

He also said he would ask the Security Council for more time to complete the searches.

"We still have quite a bit of work to do, and therefore we are going to ask for at least a few months to be able to complete our job," ElBaradei said.

In Brussels, Belgium, Blix warned Iraq Thursday it must cooperate more actively if it wants to avoid war.

"Iraq must do more than they have done so far," Blix said after briefing European Union officials.

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.

In Moscow, Russian Foreign Minister Igor Ivanov charged the United States was putting undue pressure on the inspectors.

"We are concerned about the growing pressure on the inspectors and leaders of the inspection teams from certain circles in Washington," he said.

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."

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.

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.

The Associated Press contributed to this report.