JUBA, Sept. 15 (Xinhua) -- The UN peacekeeping mission in South Sudan (UNMISS) on Saturday condemned an attack on its peacekeepers in the Southern town of Yei, where a Nepalese peacekeeper was shot and wounded in the leg by a government soldier.

UNMISS said in a statement that gun shots were fired at a convoy of four UN vehicles that were travelling from its Yei base to collect water on Saturday morning.

David Shearer, the Special Representative of the Secretary-General and Head of UNMISS, said an SPLA soldier shot directly at one of the vehicles, hitting the Nepalese peacekeeper in the leg then ran off into a crowd.

"This direct attack on UN peacekeepers here to help the people of South Sudan is unacceptable. The perpetrator must be found and held accountable by Government authorities," Shearer said.

He said the troops were unable to return fire as they did not want to risk injuring civilians, adding that the injured peacekeeper was evacuated to the UN and later airlifted to Juba for further medical treatment, the statement adds.

"This situation is evidence of a lack of command and control of armed forces which has resulted in unruly elements who continue to commit human rights abuses in the area. It is beholden on the Government to bring their forces under control," said Shearer.

South Sudan descended into civil war in late 2013, and the conflict has created one of the fastest growing refugee crises in the world.

The UN estimates that about 4 million South Sudanese have been displaced internally and externally, and the world's youngest nation has for the third year running been ranked as the deadliest for aid workers to operate.

The latest attack on the blue helmets comes less than a week after the parties to South Sudan's five-year old conflict signed a peace deal in neighboring Ethiopia on Wednesday.

The UNMISS said prior to the wounding of the peacekeeper, government soldiers had earlier fired an estimated 50 shots about 500 meters from the UN base in Yei.

"Signing of the revitalized peace agreement by all parties to the conflict three days ago heralded a time of optimism for the future. It is disheartening that, despite the new agreement, fighting is continuing in the Central Equatorian region," said Shearer.

The UNMISS senior official said all forces must disengage as required by the peace agreement and end the violence.

"The parties must also work together to build trust between themselves and with the people of South Sudan who are suffering immensely from the ongoing conflict," said Shearer.