Police in Johannesburg Monday arrested the leader of the radical Azanian Youth Organization, Thami Mcerwa, who last week threatened to disrupt concerts in South Africa by American singer Paul Simon.

Soweto police spokesman Capt. Joseph Ngobeni confirmed the arrest but said he was not yet aware of the charge.Meanwhile, organizers blamed the poor turnout at Simon's opening concerts, which were attended mostly by whites, on threats of violent protests by black militants.

About 16,000 people attended Simon's Sunday concert, leaving most of the 70,000-seat Ellis Park stadium empty. Huge banks of seats in the Johannesburg stadium were deserted.

Hundreds of police mounted guard Sunday at the stadium, but there were no protests. A small group of radical blacks protested peacefully at the first concert Saturday.