Two people were "martyred" at the scene of the demonstration in eastern Jalalabad city and their bodies were taken to the city's public health hospital, the hospital's chief director Fazel Mohammad Ibrahimi told AFP.

Another person died at the medical university hospital and a fourth dead demonstrator was taken to another hospital in the city, he added.

Forty-one injured people, four in a critical condition, were in the public health hospital and 12 were at the university hospital, while many others were treated for light injuries at both, he said.

The US State Department said late Tuesday that the Pentagon was investigating a report in US-based Newsweek magazine that interrogators in Guantanamo, Cuba, kept copies of the Koran in toilets to annoy prisoners.

Meanwhile President Hamid Karzai said that Afghan security forces were overwhelmed by the violent protests on Wednesday.

"It shows Afghan institutions are not yet ready to handle protests...That must be made better," Karzai said at NATO headquarters during an official visit to Brussels.

He said the fact that people were in the streets showed that Afghan society has evolved considerably since the fundamentalist Taliban regime was removed by a US-led military coalition at the end of 2001.

"The event this morning showed two things: one that Afghanistan is a democratic state and two, that Afghanistan as a democratic state is not yet ready with institutions to handle it."