Reinforced with newly arrived staff in Baghdad, U.N. inspectors stepped up their searches Saturday, visiting a dozen sites in Iraq -- including rooms at an infectious disease center where they were denied access a day earlier.

"Today was probably the single largest" group of sites inspected since the teams returned to Iraq on Nov. 27 after a four-year hiatus, said Hiro Ueki, a spokesman for the U.N. program in Baghdad. He said inspectors had visited a total 70 sites.

After their first known snag, inspectors revisited the Communicable Disease Control Center in Baghdad on Saturday, entering rooms that had been locked on Friday.

Inspectors said in a statement that there was no sign of tampering with seals they applied to doors and windows at the center when they were denied access. They said Saturday's inspection lasted about an hour.

Iraqi officials said the rooms had been locked because Friday, the Muslim day of prayer, is a day off for doctors and other workers who had keys.

With the arrival of 15 additional inspectors Saturday, the total now stands at 113.

Iraq received chief U.N. weapons inspector Hans Blix's demand Saturday for a list of all personnel currently and formerly associated with the country's chemical, biological and ballistic missile programs, a U.N. official said.

The U.N. Security Council resolution that ordered the resumed inspections authorizes teams to interview any Iraqi inside the country and without Iraqi officials present, or to take the person out of Iraq with his or her family.

One site visited Saturday was the main Iraqi nuclear center where nearly two tons of low-grade enriched uranium are stored. Inspection teams also went to a Scud missile facility that had been used to make bomb casings for chemical weapons before the end of the 1991 Gulf War.

Also Saturday, Iraqi Deputy Prime Minister Tariq Aziz, opening the Al-Merbad Poetry Festival in Baghdad, lashed out at the United States and Israel, saying they were bent on the destruction of Muslims.

"Imperialism as represented by the center of evil, America and its Zionist ally, are waging an oppressive aggression that targets the existence of the Islamic community and its future," said Aziz, who was wearing a military uniform. "The imminent goal is Iraq and Palestine, the ultimate goal is the whole Islamic community."

U.S. jets, meanwhile, used "precision guided weapons" against three air-defense installations Saturday morning south and east of Baghdad after Iraqi military jets violated the southern no-fly zone, the U.S. Central Command said.

"They (the Iraqi warplanes) went south. I cannot begin to ascertain what their motivation was in doing so other than plainly violating the zone," said Central Command spokesman Maj. Pete Mitchell.

U.S. and coalition aircraft have patrolled the southern and northern no-fly zones since the Gulf War ended. The zones were established to prevent Iraqi President Saddam Hussein from attacking the Kurdish minority in the north of the country and the Shiites in the south.

The inspection of the Scud complex, the government-owned al-Nasr company, 30 miles north of Baghdad, was a re-examination of the facility that also houses sophisticated machine tools that can, for example, help manufacture gas centrifuges. Such centrifuges are used to "enrich" uranium to bomb-grade level -- a method favored by the Iraqis in their bomb program of the late 1980s.

The al-Tuwaitha nuclear facility 15 miles southeast of Baghdad, contains 1.8 tons of low-grade enriched uranium and several tons of natural and depleted uranium.

U.N. nuclear agency inspectors who visited the site Saturday have said the materials are of such low radioactivity that they could not easily be turned into weapons. The uranium has been in storage since the end of the Gulf War.

Iraqi officials said the nuclear facility had been destroyed twice -- by the Israelis in 1981 during the Iran-Iraq war and by the U.S.-led coalition that drove Iraqi forces out of Kuwait during the Gulf War.

Recent satellite photos show four new buildings at the site suspected of housing new nuclear projects. The Iraqis, who deny have weapons of mass destruction or programs to build them, say the buildings are for environmental, medical and agricultural research.

In the first round of inspections in the 1990s, after Iraq's Guld War defeat, the United Nations destroyed tons of Iraqi chemical and biological weapons and dismantled Iraq's nuclear weapons program.

Recently published British and U.S. intelligence reports said new construction at old weapons sites and other activities suggest the Iraqis may have resumed making weapons of mass destruction.