Mainstream Islamic leaders in Yogyakarta are claiming the right to oversee the activities of Ahmadiyah groups after local adherents of the sect were threatened by an angry mob on Friday.

"We will continue to supervise all activities of GAI [Indonesian Ahmadiyah Movement] and Jamaah Ahmadiyah Indonesia," the head of the Yogyakarta branch of the Council of Ulema (MUI), Thoha Abdurahman, said on Sunday.

On Friday, hundreds of people calling themselves Front Umat Islam made an angry visit to interrupt an Ahmadiyah religious study session held at the Piri vocational high school in Yogyakarta.

Thoha blamed the Ahmadis themselves for the incident, saying they had breached an agreement to inform the MUI of all their activities and the content of any teaching materials.