Afghan authorities said Saturday that they had detained a group of university professors from the eastern city of Jalalabad on suspicion that they orchestrated violent anti-American riots there last month on behalf of an extremist Islamic group.

Interior Minister Ali Ahmad Jalali said the professors were members of Hezb-i-Islami, a group whose fugitive leader, Gulbuddin Hekmatyar, is an ally of the Taliban militia.

Jalali said the professors had been brought to the capital for questioning and were "under investigation." He also hinted that the protests were instigated on orders that originated abroad, but said he could give no details.

The protests were sparked by a news report that guards at the U.S. prison at Guantanamo Bay, Cuba, had desecrated the Koran. An initial demonstration May 10 in Jalalabad was peaceful, but the next day, a similar protest turned violent, and at least 16 people were killed in protests in the ensuing days.

Jalali also said the government had released the imprisoned mother of a man suspected of kidnapping an Italian aid worker, Clementina Cantoni, who was set free Thursday. Jalali denied that it was part of a deal to win Cantoni's release.

Jalali said Cantoni's captor, who called himself Timor Shah, was part of a criminal gang that was linked to the previous kidnapping and killing of a Kabul businessman's son. He said authorities had detained 17 people, including Shah's mother, in the first case, and that the kidnapper abducted Cantoni on May 16 in hopes of exchanging her for the captives.

The government detained 11 people in connection with Cantoni's kidnapping but then freed three of them, Jalali said.

-- N.C. Aizenman