At his heavily guarded presidential office in Kabul, he blamed "enemies of peace" and "enemies of stability" for violently subverting students' protests over recent reports that American interrogators at Guantánamo Bay, Cuba, had desecrated a Koran.

"Who are they who have such enmity with Afghanistan, a nation that is begging for money to build the country and construct buildings, and during the night they come and destroy it?" he said, pointing out that 200 Korans had been burned when a public library in Jalalabad was set on fire.

"In all the Islamic world the students were all studying, Afghan students were encouraged to rise up and start demonstrations," he said, "and then other elements got into the demonstration and in the name of Afghanistan's students and boys, destroyed Afghanistan's property."

He mentioned no names, but seemed to outline the agenda of Al Qaeda, elements in Pakistan and renegade Afghan commanders who want to keep Afghanistan in chaos.

But here in Ghazni, a town south of Kabul that was the scene of some of the worst violence, the analysis of who was behind the violence - which on Friday left a police sergeant and three civilians dead and a police chief and many others injured - was more nuanced. Townspeople and officials said demonstrators' anger had been genuine, inspired by outrage and stirred up by local mullahs during Friday Prayer. But they acknowledged that "troublemakers" may have taken the opportunity to shoot at the police.

Mr. Karzai said he could well understand the Afghan people's anger at the reported desecration, a Koran flushed down a toilet. But he urged people to await the outcome of the investigation that the Bush administration has promised.

"Without doubt it is difficult for all the world's Muslims and also for all the Afghan people who love their faith, and Afghanistan sacrificed a lot in this regard, they fought against the Russians and millions of people died in that struggle," he said. "If it is true that it happened, we will ask the U.S. that the perpetrator be punished."

Mr. Karzai also criticized the destruction of a cellphone tower that had been knocked down south of Kabul. That, he said, set back Afghanistan's steps to stand on its own feet and have its own telephone system, rather than having to route calls through neighboring Pakistan.

"What's the point of bringing down the telephone tower?" he asked. "Was it friendship with Islam? Was it friendship with Afghanistan?" he said the demonstrations were an attack on Afghanistan and its progress. "It was to defame Afghanistan and to stop its partnership with the world," he said.

Several more demonstrations took place Saturday in the southern border town of Spinbaldak, and in Zabul, Farah and Badghis Provinces, but all passed peacefully, Reuters reported. In Ghazni, tensions remained high. Shops closed early and streets emptied as rumors spread of another stone-throwing demonstration.

In the violence Friday, even the governor, Hajji Asadullah Khan, was hit in the head by a rock from the crowd. Doctors at the town hospital said they had treated 19 wounded.

Among them was a teenager, Ghulam Sakhi, who was pushing his wheelbarrow down the street on his way home when he was shot. "I was shot from the back; I saw it was a soldier of the National Army," he said, wincing on his hospital bed.

Doctors said they had also treated a soldier of the Afghan National Army who was injured by a rock. They said they had to hide him in a room in the women's ward. "The people were very angry," said Muhammad Ilyas, 22, a metalworker who took part in the demonstration.

The demonstrators, infuriated by accounts that Americans had also burned copies of the Koran, burned pictures of President Bush, he said. Townspeople interviewed were sometimes confused about details, but they were convinced that Americans had done something terrible against their religion.