LUSAKA, ZAMBIA, JUNE 28 -- President Kenneth Kaunda, facing the most serious crisis in his 26-year rule, toured central Lusaka today after food riots in which at least 24 people were killed. Meanwhile, demonstrating university students called on him to resign.

This south-central African nation was calm today for the first time since Monday, when riots erupted over food price increases and Kaunda's one-party rule. Thousands of residents watched quietly as Kaunda inspected the central shopping district where goods worth thousands of dollars were looted in three days of rioting.

Kaunda, who blamed the riots on political opponents seeking to overthrow him, said he would announce on Friday the dates of a referendum on introducing multi-party rule, which he opposes. In May, Kaunda promised the referendum but set no date.

Hospital sources said about 150 people were injured, mostly by gunfire, during the riots.

Thousands of residents flooded into Lusaka's city center, which had been sealed by police and troops when the government imposed a curfew Tuesday evening.

Troops with fixed bayonets stood guard on the main roads, keeping people off some thoroughfares, and cordoned off traffic on the main shopping street, during Kaunda's one-hour visit.

Most businesses were closed and the crowds watched quietly as Kaunda moved from shop to shop with an entourage of officials.

The quiet of central Lusaka contrasted sharply with a noisy demonstration at the University of Zambia, two miles away, where about 1,000 students shouted anti-government slogans and called on Kaunda to resign. Some slogans pasted on buildings read: "Kaunda don't shoot, resign" and "Hang Kaunda."

In a radio and television address Wednesday night, the Zambian leader said there was no alternative to the government's having raised the cost of a 55-pound bag of cornmeal from $2.79 to $6.56. "Our economic recovery program is assured. Nothing at all can stop it," he said.

Zambia, one of Africa's richest nations when it gained independence from Britain in 1964, has a $7.2 billion foreign debt incurred to sustain growth after earnings from copper, the main export, started falling in the early 1970s.

The country is working closely with the International Monetary Fund and the World Bank to cut public spending and free price controls.

Kaunda has ruled since independence and abolished a multi-party system in 1972.