By Magdi Abdelhadi BBC Arab Affairs editor

Saudi Arabian authorities have revealed that 90 Saudi nationals are to stand trial accused of membership of the al-Qaeda network.

This would be the first prosecution in Saudi Arabia of alleged members of Osama Bin Laden's organisation.

The interior minister, Prince Nayef Bin Abdulaziz, told the Saudi newspaper Okaz that more than 250 detainees were still being investigated on similar charges.

There was evidence the 90 Saudis had joined al-Qaeda, the prince also said.

But he gave no further details about the charges or the date of the trial.

Saudi Arabia says no terrorist groups operate on its soil

Prince Nayef did not say for how long the other 250 suspects had been detained or the total number of Saudis held on similar charges.

He reiterated a well-known Saudi position that there were no terrorist organisations operating on Saudi soil, only small groups of no more than ten people each.

Prince Nayef accused what he described as foreign organisations of infiltrating Saudi society and brain washing its youths.

Saudi authorities have repeatedly rejected accusations in American media that the country's puritanical brand of religion, known as Wahhabi Islam, is a breeding ground for Islamic militancy.