Ankara, Turkey — Turkey's military authorities ordered the country's most prominent Islamic campaigner, Necmettin Erbakan, held in custody pending charges that he worked to undermine the secular nature of the state. Mr. Erbakan, who had been released Sunday, was one of four top politicians held by the military after Sept. 12 coup. Another minority leader, Alpaslan Turkes, an extreme rightist, has remained in detention. Charges against him include incitement to massacre and inciting people against one another, charges that could bring the death penalty. The two most senior politicians, former Prime Minister Suleyman Demirel and Bulen Ecevit, were released over the weekend and face no charges.