KABUL, Afghanistan - Helmeted riot police fired live ammunition to disperse student demonstrators yesterday during a second day of clashes over conditions at Kabul University, protests that point to some of the wider frustrations building within Afghan society a year after the collapse of the Taliban.

No casualties were confirmed in the conflict yesterday, but as many as four students had been killed by police gunfire Monday night.

The students attempted to take to the streets yesterday to protest the deadly shootings by police trying to quell an apparently impromptu demonstration Monday night. The demonstration came about when dormitory food ran out for 400 students waiting in line to break their daylong Ramadan fast.

When students resumed their protests yesterday, the crowd was blocked by police and firefighters who first used water cannons, then live bullets, to try to disperse the hundreds of demonstrators who were throwing stones and bottles and chanting slogans demanding that the police who shot the students be brought to justice.

The university campus was calm by nightfall after President Hamid Karzai promised to investigate grievances and to call to account the police who opened fire. But tensions remained high, and several students said the protests would continue until the police responsible were brought to justice.

State television confirmed the deaths of two students late Monday, but other students and an army officer who witnessed the protest said four students had been shot dead in the Monday clash. Several students and police officers were reported injured.

Police said no arrests had been made. While the protests were aimed at the ineptitude and alleged corruption of university administrators, the violence has exposed some of the rifts and rising frustrations within Afghanistan that threaten Karzai's fragile U.S.-backed administration, even in the heart of Kabul.

The students say they were demonstrating only against conditions at their government-run dormitory, which, like much of Kabul, has been mostly without water and electricity for weeks.

Police officials said they suspect former supporters of the Taliban had deliberately provoked trouble as a way of marking the anniversary overnight yesterday of the Taliban's retreat from Kabul.

"The students face very big problems. They don't have power, they don't have blankets, they don't have water, they don't have enough food," said Gen. Afzal Amal, who was supervising the heavily armed police force surrounding the student dormitory. "But we also think there was a political element to this. Today it is a year since the Taliban left Kabul, and there may be some people among the Taliban who want to mark this first anniversary by causing problems for the government."

Liz Sly writes for the Chicago Tribune, a Tribune Publishing newspaper.