The assembly vote, by acclamation, followed South Sudan's independence proclamation in the capital Juba on Saturday, after its people voted in a January referendum to break away from Sudan — a decision accepted by Khartoum.

Applause broke out in the assembly as South Sudan became the first country to join the world body since Montenegro in 2006. The Security Council, which rules on all UN membership applications, had recommended the admission on Wednesday.

"Welcome, South Sudan. Welcome to the community of nations," UN Secretary-General Ban Ki-moon said. Assembly President Joseph Deiss said it was a "historic and joyous moment."

The South Sudan flag — black, red and green stripes, overlaid with a blue triangle and gold star — was later hoisted outside UN headquarters in New York.