KIGALI, Rwanda — Rioters rampaged through the capital of Sudan yesterday, smashing cars and shops in violence that officials said left at least 36 people dead, as news spread that John Garang, a prominent rebel leader and the newly installed first vice president of Sudan, had been killed in a helicopter crash late Saturday.

World leaders quickly urged Sudanese factions to carry on the peace process in which Garang, 60, played a major role. His triumphal move three weeks ago to the capital, Khartoum, marked the end to a 21-year civil war between Sudan's Muslim North and the largely Christian and animist South — a conflict separate from that in the Darfur region in western Sudan, where violence continues. The Khartoum government called for three days of mourning, and Garang's longtime top deputy was named to replace him as head of the Sudan People's Liberation Movement (SPLM).

Garang's widow also urged calm, addressing the public by radio, and asked that the peace deal continue. In an interview, she said that despite rumors, there was no evidence of foul play in her husband's death.

"We want to keep his legacy alive," Rebecca Garang said by telephone from southern Sudan. "Keeping the peace is how we can honor his memory."

But across Sudan, where people were beginning to lay down their guns, debate a new constitution and draw up plans to build schools and hospitals after years of war and deprivation, many now were asking what effect Garang's death would have on the country's fledgling peace process.

Garang died when his helicopter crashed because of bad weather just a few miles from his base, New Site village, in southern Sudan. He was returning from an official visit with Ugandan President Yoweri Museveni at his ranch.

More than a million people celebrated at the historic ceremony in Khartoum on July 8, when the burly and bearded Garang was sworn in as vice president under a U.S.-backed peace deal between the Arab-led Khartoum government and the largely African rebel forces of the marginalized South that had long fought for separation.

Yesterday, Sudanese officials said the peace deal must be upheld. President Omar Hassan Bashir, the man Garang once proclaimed as his enemy, called for calm and said in a statement that the country faced "a difficult test." A funeral was expected to be scheduled at New Site.

U.N. Secretary-General Kofi Annan expressed "great sorrow" at Garang's death and urged Sudanese leaders to "continue with the process of reconciliation." Annan said Bashir assured him he would work "very, very closely" with Garang's movement to advance the peace process. "We should all do whatever we can to ensure that it doesn't unravel," Annan said.

The United States drafted a U.N. Security Council statement lauding Garang for his role in ending Sudan's civil war and calling on Sudanese people "to honor his memory by restoring peace and calm throughout Sudan."

In Khartoum, however, widespread rioting was reported. The airport was closed, and diplomats said they heard gunfire throughout the capital. There also were reports of unrest in areas of southern Sudan.

"There are massive riots here. There's a lot of destruction of property. It has now gone to also burning vehicles, instead of just smashing windows. We received reports that the army now is deploying to get the situation under control," said Col. Bjarne Giske, head of the Joint Monitoring Commission, a U.S.-backed force, speaking from Khartoum.

Some rioters accused Khartoum of plotting a coup to kill Garang, shouting, "Killers and murderers!" observers reported.

Hordes of young men filled downtown Khartoum, smashing car windows and tearing off doors, setting fires, looting shops and, in some cases, chasing pedestrians away with stones. One group stopped a passing journalist and asked, "Are you with us or against us?" and demanded to search his briefcase before they let him pass.

The government reported that 36 people were killed and approximately 300 were injured in the riots. No information was available on how many of those killed were security forces and protesters.

Police and soldiers used tear gas to disperse the larger crowds of Garang supporters, and by midday downtown was nearly empty. The streets leading to the Republican Palace were sealed, and many residents and shopkeepers stayed indoors.

The mood quieted but remained tense after officials imposed a 6 p.m. to 6 a.m. curfew. A Western diplomat reported the streets were "empty, very quiet," but that there had been "lots of looting, burning, stoning and some deaths." The diplomat said there was "great despondency" among both southern and northern Sudanese.

In Juba, one of southern Sudan's largest cities, soldiers once under Garang's control started looting Arab-owned businesses, according to television reports. They demanded the expulsion of thousands of Sudanese army troops. Aid workers in southeastern Sudan reported at least one person had been killed in rioting.

In Nairobi, Kenya, wailing mourners gathered outside the headquarters of Garang's SPLM, which was based there during the civil war.

At least 2 million people were killed and millions were displaced in Sudan's civil war. Under the peace agreement, residents of the south will vote in six years to determine whether they want to secede from the rest of the country.

The area is one of the poorest places on Earth; children routinely die of malaria and other diseases, such as guinea worm, because of lack of health centers in 90 percent of the south.

Information from The Associated Press is included in this report.