Binyamin Netanyahu has offered good wishes to the world's newest country following its independence on July 9 at midnight.
The Republic of South Sudan was created in 2005 in a peace agreement ending decades of civil war. The Israeli Prime Minister said Israel recognised the new state and added: "We wish it much success."
He also said Israel "would be pleased to co-operate with it in order to ensure its development and its prosperity" and described it as "a peace-seeking country".
There were celebrations in Tel Aviv, where many refugees escaping the conflict in the Darfur region of Sudan now live.
