MONROVIA, Liberia (AP) _ The bloodiest barrage in days sent shells crashing into U.S. Embassy grounds and a school packed with refugees in the rebel-besieged capital Friday _ leaving people wondering why a long-hoped-for U.S. peace deployment was coming only after so high a toll.

President Bush's order of ships and troops to Liberia's coast was broadcast over the radio here as refugee families gathered broken bodies of men, women and children. All were victims of a daybreak mortar attack that killed at least 12 and wounded more than 150.

``Why so late, when people are dying?'' Momo Barley asked in the streets around the U.S. Embassy, the densely populated, rocky hilltop neighborhood overlooking the Atlantic that took the brunt of Friday's 10-minute pounding by up to 20 mortar rounds.

``This is another promise again,'' refugee Sylvester Blamo, 30, said in the same neighborhood, as aid workers tended to lumpily filled body bags.

Monrovia's residents have prayed, even pleaded, for U.S. deployment in the American-founded nation over two months as rebels pressed home their 3-year war to drive out Liberia's warlord-turned-president, Charles Taylor.

A few weeks ago, even false rumors of U.S. Marines landing were enough to set off joyous celebrations, with dancing and singing in the streets.

There was no such immediate outbreak of joy in the numbed city Friday. Three waves of attacks have killed hundreds in the capital. About 1.3 million residents hang on, gripped by hunger, thirst, epidemics and fear.

``I want to tell George Bush to do something hurriedly, very fast and quickly,'' Emmanuel Sieh, 28, cried earlier Friday, as crowds spilled out into the streets following a fierce 20-missile barrage in 10 minutes.

One shell Friday struck inside the U.S. Embassy compound, exploding harmlessly on rocky ground, a U.S. official inside said.

Other rounds wrought carnage among refugees, who have crowded around the embassy by the thousands in hope of protection through proximity to the Americans.

One shell at the beginning of the attack slammed into a yard where two boys stood brushing their teeth, killing both.

Blocks away, another shell crashed into the yard of a school where hundreds of people have taken refuge.

The round killed seven refugees outright; an eighth was reported dead at an international aid group's tent clinic.

At the school, wailing crowds surrounded the dead. Victims' flip-flops lay discarded, soaking in pools of blood. One body, that of a boy in his early teens, lay curled in a corner.

Cradling a 2-week-old baby, a woman sobbed uncontrollably next to a body bag holding the corpse of her sister, the child's mother.

``What do they want to achieve?'' Peter Garwah, 27, cried out, before a new mortar round sent terrified survivors scrambling for cover under schoolhouse tables or pressing, screaming, against classroom walls.

``Innocent people are dying, not soldiers.''

The casualty toll, reported by aid clinics and Monrovia's overwhelmed main hospital, was likely to climb far higher.

An ambulance brought gravely wounded people to the open-air tent hospital run by Medicins Sans Frontieres, also known as Doctors Without Borders.

Workers ferried in the wounded _ a man with a mangled leg; a woman with her intestines spilling out.

Rebels declared they welcomed word of the U.S. deployment.

``I think that's what all Liberians want to hear. We applaud that,'' said Charles Benney, an envoy for rebel at off-and-on peace talks in Accra, Ghana.

``We've been waiting for the Americans to make a commitment for a long time,'' Benney said.

Taylor's government's welcome was far more grudging. Bush has declared that Taylor must step down as part of any peace effort.

``We have always recognized that the United States is the superpower of the world and their presence in the international peacekeeping force in Liberia might make things easier to disarm the rebels,'' said Vaanii Paasawe, Taylor's spokesman.

``We are only surprised that as a democracy itself, the United States could play the role it has in Liberia,'' Paasawe said.

West African leaders have promised a multinational force for Liberia since soon after rebels opened offensives in June on the city of 1 million, now crowded with hundreds of thousands of refugees.

Taylor, sought by a U.N.-backed court for alleged war crimes in neighboring Sierra Leone, has promised to step down when foreign peacekeepers arrive. But he has repeatedly hedged on promises since June to cede power.

In Sierra Leone, a lawyer for Taylor filed a motion Wednesday challenging the jurisdiction of the court.