A rocket attack on Iraq's heavily fortified Green Zone killed four Filipino contractors working for the U.S. government, the American embassy said Thursday. It was the third straight day that extremists used rockets or mortars to hit the area where Iraq's parliament meets.

The embassy said Wednesday's attack left it "with a profound sense of sadness and regret" over the loss of Filipinos who "were integral members of our embassy community."

The brief statement provided no other details about the attack, including the time or location of the explosion in the Green Zone, which is home to the U.S. and British embassies and thousands of American troops. Such information often is withheld to avoid giving extremists information for future attacks on the area.

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However, the whistle of suspected rockets had been heard passing over the Tigris River in central Baghdad and into the Green Zone on Wednesday evening. It was the third straight day that the zone was hit by rockets or mortars, heightening concerns about security in the area.

In other violence in Iraq on Wednesday, a suicide car bomber struck in the main Shiite district of the capital, killing at least nine people, as the U.S. military said its troop buildup in Baghdad was nearly complete.

Three more U.S. soldiers were killed by bombs in the capital. At least 85 Iraqis were killed or found dead nationwide Wednesday, police reported. Those included eight people who lost their lives when a roadside bomb destroyed their minibus about 20 miles south of Baghdad.

Also Wednesday, two U.S. soldiers were killed and two others were wounded when a bomb devastated their vehicle in southern Baghdad, the U.S. command said. Another soldier died in a blast in western Baghdad, the command said.

At least 3,354 members of the U.S. military have died since the Iraq war started in March 2003, according to an Associated Press count. Last month, at least 104 U.S. service members died — the highest monthly figure since December.

Complete coverage is available in FOXNews.com's Iraq Center.

Insurgents and militia fighters routinely fire rockets and mortars into the Green Zone, a sprawling complex which is surrounded with tall cement blast walls on the west bank of the Tigris, but the attacks seldom cause casualties or damage because they are poorly aimed and the zone contains much open space.

But two Americans — a contractor and a soldier — were killed in late March in a rocket attack on the area and two suicide vests were found unexploded less than a week after that.

The adequacy of security in the vast area in central Baghdad more recently came into question in the aftermath of the April 12 suicide bombing in the Iraqi parliament building's dining hall. One lawmaker was killed in the blast, which was claimed by an al-Qaida-led amalgam of Sunni insurgents.

On Wednesday, Rear Adm. Mark Fox, a U.S. military spokesman, told a news conference that the latest round of Green Zone attacks appears to be part of an overall strategy by extremists "to score a spectacular hit or try to obtain some sort of a headline-grabbing direct hit."

In response to the killings, Philippine President Gloria Macapagal Arroyo called for a quick reassessment of whether Filipino workers in Iraq need to be repatriated.

Arroyo also ordered diplomatic and labor officials to immediately bring home the bodies of the contractors, who had worked for the U.S. government in Baghdad's heavily fortified Green Zone, her spokesman, Ignacio Bunye, said.

"The president is saddened at the news," Bunye said.

The Philippines banned deployment of workers to Iraq after insurgents abducted Filipino truck driver Angelo de la Cruz in July 2004.

To save his life, Arroyo granted the kidnappers' demand for the early withdrawal of a small Philippine peacekeeping contingent from Iraq — a decision strongly criticized by Washington and other allies, but applauded at home.

A second Filipino, accountant Robert Tarongoy, also was abducted by Iraqi militants. He was freed in June 2005 after almost eight months in captivity.

About 5,000 to 6,000 Filipinos are employed in U.S. military camps across Iraq, mostly as cooks and maintenance personnel. A smaller number work as bodyguards for businessmen. Most were already in Iraq when the Philippine government imposed the deployment ban.

Despite the ban, many Filipino workers are believed to have slipped into Iraq through neighboring countries such as Jordan, prompting the government to appeal to those countries to help block such passage.