East African heads of state admitted South Sudan as a member the regional bloc Inter-Governmental Authority on Development (IGAD) Friday, some four months after the nation proclaimed independence.

The Republic of South Sudan ... have taken a pro-active measure for membership to IGAD, and their membership was approved by the summit, Mahboub Maalim, IGAD executive secretary, told reporters following a meeting of heads of state.

South Sudan was admitted to the African Union some two weeks after its independence on July 9, the culmination of a peace agreement following a brutal two-decade civil war.

The country is one of the world's poorest and has inherited a string of disputes with its northern neighbour after its people voted in a January referendum to break away from Sudan -- a decision accepted by Khartoum.

Representatives of the two countries have resumed AU-mediated talks this week on solving outstanding issues such as demarcation of their porous border and oil revenue-sharing.

The U.N. General Assembly admitted South Sudan on July 14 as the 193rd member of the United Nations.

(Reporting by Aaron Maasho; Editing by George Obulutsa)