HAMPTON, Va. — Senator Obama, a Democratic presidential hopeful, said yesterday that the Bush administration has done nothing to defuse a “quiet riot” among blacks that threatens to erupt just as riots in Los Angeles did 15 years ago.

The first-term Illinois senator said that with black people from New Orleans and the Gulf Coast still displaced 20 months after Hurricane Katrina, frustration and resentments are building explosively as they did before the 1992 riots.

“This administration was colorblind in its incompetence,” Mr. Obama said at a conference of black clergy, “but the poverty and the hopelessness was there long before the hurricane. All the hurricane did was to pull the curtain back for all the world to see.”

Mr. Obama’s criticism of Mr. Bush prompted ovation after ovation from the nearly 8,000 people gathered in Hampton University’s Convocation Center, particularly when he denounced the Iraq war and noted that he had opposed it from the outset.

Repeatedly, he referred to the riots that erupted in Los Angeles after a jury acquitted four police officers of assault charges in the 1991 beating of Rodney King, a black motorist, after a high-speed chase. Fifty-five people died and 2,000 were injured in several days of riots in the city’s black neighborhoods.

“Those ‘quiet riots’ that take place every day are born from the same place as the fires and the destruction and the police decked out in riot gear and the deaths,” Mr. Obama said. “They happen when a sense of disconnect settles in and hope dissipates. Despair takes hold and young people all across this country look at the way the world is and believe that things are never going to get any better.”

He argued that once a hurricane hits or a jury renders a not guilty verdict, “the frustration is there for all to see.”

Mr. Obama, who is bidding to become the first black president, raised issues that roused the crowd: increasing the minimum wage and teacher pay, funding for public schools and college financial aid for the poor, ending predatory lending, and expediting the reconstruction of New Orleans and the Mississippi coast.

Mr. Obama noted that during the Los Angeles riots, a bullet pierced the abdomen of a pregnant woman and lodged in the elbow of her fetus. The baby was delivered by caesarian section, the bullet was removed, and the child, Jessica Glennis Evers-Jones, has only a small scar on her arm to show for it.