Secretary-General Ban Ki-moon late Friday welcomed the agreement signed in Addis Ababa, Ethiopia, earlier in the day, to resolve the crisis in South Sudan, his press office said in a statement. The agreement, signed, under US and EU pressure, by President Salva Kiir and his rival former Vice President Riek Machar, called for an immediate ceasefire, the formation of a transitional government, the drafting of a new constitution and new elections. "He (Ban) demands that the parties immediately translate these commitments into action on the ground, in particular the cessation of all hostilities," the statement urged, reiterating the UN steadfast commitment to the South Sudanese people. Ban commended the Inter-Governmental Authority on Development (IGAD), and in particular its Chairman Ethiopian Prime Minister Hailemariam Desalegn, for its ongoing efforts to mediate a peaceful and sustainable end to the five-month old conflict. A political crisis erupted in the country on December 15 when President Kiir, supported by government forces loyal to his Dinka tribe, accused his rival Machar, supported by troops loyal to the Nuer tribe, of staging an attempted coup. Fighting between the two tribes subsequently picked up pace. Ban visited the newly independent country earlier this week and urged the rival leaders to sit down together for talks. He also visited the Tomping civilian protection site, home to some 21,000 South Sudanese civilians. The in-fighting has left thousands dead and refugees. Tens of thousands were lucky to be alive after they sought refuge in UN bases around the country. The UN Mission in South Sudan accused both parties on Thursday of gross human rights abuses, including rapes, mass killings and torture, and insisted that the civilians were not caught up in the violence but rather directly targeted, often along ethnic lines.