By mid-April, Mostar had become a divided city with the majority Croat western part dominated by the HVO, and the majority Bosniak eastern part dominated by the ARBiH. The Battle of Mostar began on 9 May when both the east and west parts of the city came under artillery fire. Fierce street battles followed that, despite a ceasefire signed on 13 May by Milivoj Petković and Sefer Halilović, continued until 21 May. The HVO established prison camps in Dretelj near Čapljina and in Heliodrom, while the ARBiH formed prison camps in Potoci and in a school in eastern Mostar. The battle was renewed on 30 June. The ARBiH secured the northern approaches to Mostar and the eastern part of the city, but their advance to the south was repelled by the HVO.