South Sudan's President Salva Kiir has told the army not to retaliate against rebels in order to honour the latest cessation of hostilities agreement signed last Thursday in Ethiopia.

President Kiir said his government was committed to the ceasefire pact that came into effect on Sunday but was shattered hours later when the military clashed with rebels in Yei River and Unity States.

Both sides accused the other of starting the fighting.

Mr Kiir expressed disappointment over the breach of the truce.

“Shortly the international community will say all sides are guilty of violations of ceasefire. But now, we will keep our words. Let me assure you that we are not going on the offensive,” he said.

He urged international monitors mandated by the August 2015 peace agreement to single out the violators.

President Kiir reiterated that he had issued orders for the immediate implementation of the ceasefire so as to guarantee the safety of civilians and humanitarian services in the war-torn country.

Earlier this week, the President said his government's top priority in 2018 was to restore peace and unity among all communities in the country.

South Sudan, which attained independence in 2011, has been in a four-year civil war.

More than 100,000 people have lost their lives in the conflict, according to the International Crisis Group.

Over two million South Sudanese have become refugees, while another one million people remain internally displaced, according to the UN.