The United Nations chief is urging regional and international leaders to prevent South Sudan from falling “over the abyss” into another civil war, and to speak with one voice to support a return to peace.

An attack on a U.N. helicopter has highlighted rising tensions in the world’s youngest country, where a seven-year-old peace deal looks ever more fragile.

United Nations Secretary-General Antonio Guterres said on Friday that a peace agreement in South Sudan was in a shambles, telling the country's leaders to put down the weapons and put all the people of South Sudan first.