Every Friday dervishes gather an hour before sunset around some of the big mosques in Khartoum and Omdurman. A circle is formed and the ritual begins. The ceremony starts with the Madeeh - chanting words of gratitude to the Prophet Mohammed. The audience interacts with the chanters, dancing to the rhythms of the percussion instruments. Then comes the Zikr, in which the dervishes repeat the word 'Allah' many times. The dervishes start whirling around inside the circle. With the music, the fragrance of burning frankincense, the endless repetition of religious chants, and the dizziness, they go into a state of trance. According to ancient belief, Sufism is about the purification of the soul in pursuit of inner peace. Although Sudan is in many ways a male-dominated society, women find themselves a place in the crowd. They gather in one corner wearing bright, colourful robes. At the close of the ceremony, just before sunset, one of the dervishes walks round the gathered audience with frankincense, which is considered to be a type of blessing to the faithful.