On the same day that President George W. Bush told an audience in Ohio that security gaines are being made in Iraq, the State Department has instructed all personnel at the U.S. Embassy in Baghdad not to leave reinforced structures due to incoming insurgent rocket fire that has killed two American government workers this week.

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The the department also said employees are required to wear helmets and other protective gear if they must venture outside even in the heavily fortified Green Zone and strongly advises them to sleep in blast-resistant locations instead of the less secure trailers that most occupy.

"Due to the continuing threat of indirect fire in the International Zone, all personnel are advised to remain under hard cover at all times," it says. "Personnel should only move outside of hard cover for essential reasons."

"Essential outdoor movements should be sharply limited in duration," the memo says, adding that personal protective equipment "is mandatory for all outside movements."

"We strongly recommend personnel do not sleep in their trailers," it goes on to say, offering space inside the Saddam Hussein-era palace that is the embassy's temporary home as well as room at an as-yet uncompleted new embassy compound and a limited supply of cots.

The memo was sent after a second American citizen was killed by a rocket attack in the Green Zone on Thursday. A U.S. citizen military contractor died of his wounds on Monday after being severely injured with four others in an attack.

Bush told a crowd at Wright-Patterson Air Force Base in Dayton on Thursday that the troop surge in Iraq has resulted in significant security gains for the country.

"They're trying to build a modern democracy on the rubble of three decades of tyranny, in a region of the world that has been hostile to freedom. And they're doing it while under assault from one of history's most brutal terrorist networks," Bush said. "When it takes time for Iraqis to reach agreement, it is not foot-dragging, as one senator described it during Congress' two-week Easter recess. It is a revolutionary undertaking that requires great courage."

Within weeks, Bush is expected to endorse the recommendations of Gen. David Petraeus, the top U.S. commander in Iraq. Petraeus has proposed a pause in troop cutbacks to assess the impact of having withdrawn five combat brigades since December. He has argued that it would be reckless to shrink the American force so rapidly that the gains achieved over the past year are compromised or lost entirely.

Bush said the number of sectarian attacks in the volatile Anbar province have "plummeted" since the surge.

Recent news that the U.S. death toll in Iraq hit 4,000 has again turned a spotlight on the conflict, which is entering its sixth year.

As Bush arrived, about 30 protestors demonstrated outside the museum, carrying signs that read, "Shame," and "This is not Bush county. This is our country."

At least 16 rockets were fired into the Green Zone from surrounding Baghdad districts in four separate attacks during the morning and early afternoon Thursday, the U.S. military said. Attacks were also staged in Tikrit and Salahuddin.

The attacks killed one civilian and wounded 14, a U.S. military spokesman said. In addition, three indirect-fire attacks also struck two U.S. forward operating bases and one joint security station east of the Tigris River, injuring four U.S. soldiers. Five mortar rounds struck two joint security stations and a citizen security group checkpoint in West Rashid, wounding three Iraqi security volunteers.

Iraqi officials reported that more than 17 people were killed in overnight clashes in Baghdad's Sadr City district.

"These rogue elements are haphazardly firing rockets and mortars, killing and injuring innocent Iraqi and governmental civilians," said Col. Allen Batschelet, chief of staff of Multinational Division Baghdad.

Heavy gunfire and explosions resounded across the oil port city of Basra. The city's police chief escaped an assassination attempt late Thursday but three of his guards were killed in the roadside bombing.

Iraqi government troops have faced stiff resistance in neighborhoods controlled by the Mahdi Army in Basra, Iraq's second-largest city, 340 miles southeast of Baghdad. Residents spoke of militiamen using mortar shells, sniper fire, roadside bombs and rocket-propelled grenades to fight off security forces.

A Pentagon official said Wednesday that reports from the Basra area indicate that militiamen had overrun a number of police stations. The official spoke on condition of anonymity because he was not authorized to discuss the matter publicly.

Street battles that started Tuesday in Basra and Sadr City have spread to several other neighborhoods and southern cities, leaving more than 200 dead, including civilians, Iraqi troops and militants. That three-day figure was a rough estimate provided by police and hospital officials who could not give a more specific breakdown.

Al-Maliki is personally overseeing operations against Shiite militias dominated by followers of radical cleric Muqtada al-Sadr. Al-Maliki is promising to pursue his fight against Shiite militias in Basra to "the end."

He warned gunmen Wednesday in Basra to surrender their weapons by Friday or face harsher measures.

However, government troops in Basra have been having trouble making inroads into neighborhoods that the Mahdi Army has controlled for years.

The U.S. contends the offensive is targeting only rogue fighters.