Cairo, April 17 : Egyptian President Abdel-Fattah al-Sisi and his South Sudanese counterpart Salva Kiir called for an "immediate ceasefire" in neighbouring Sudan during a phone talk. Stressing the seriousness of the ongoing military clashes between the Sudanese Army and the paramilitary Rapid Support Forces (RSF), the two leaders expressed their readiness to mediate for making peace between the fighting parties in Sudan, the Egyptian presidency said in a statement on Sunday. Sisi and Kiir warned the Sudanese parties that "escalation of violence will only lead to more deterioration of the situation, which could spiral out of control," according to the statement. "Solidifying security and stability is the key guarantor for completing the trajectory of political transition and realising construction and development in Sudan," the two leaders emphasised. Clashes erupted in the capital Khartoum and adjoining cities on Saturday morning, after days of tension over the RSF's integration into the Army, Xinhua news agency reported. At least 56 civilians were killed in the fighting and hundreds of people were wounded, according to Sudanese medics. /IANS