South Sudan's presidency has justified the unexpected sacking of oil minister Ezekiel Lol Gatkuoth while on a trip abroad.

The president’s spokesman Ateny Wek told Radio Tamazuj on Thursday that Kiir’s decision to remove Ezekiel was informed by need to appoint a new minister.

“These are normal routine changes that happen,” Ateny said.

When asked about the reason for the sacking of the petroleum minister while on a mission, Ateny said:” He [Ezekiel] was supposed to return from the official mission to Russia but he delayed. The former minister’s trip to Nigeria had nothing to do with his job.”

“After the Economic Forum in Russia ended, he went to Nairobi and then to Nigeria for a private mission,” he explained.

Ateny, who is also the presidential press secretary, said it is the duty of the president to remove and appoint government officials.

The presidential decree on Wednesday night gave no reason for Ezekiel's sacking.

There had been no indication that Mr Ezekiel - who was sacked while on a trip abroad - was about to lose his job.

Kiir appointed Awou Daniel Chuang, the director general at the petroleum ministry, to replace Mr Ezekiel.

Ezekiel was appointed oil minister in August 2016.

The former oil minister, who is a strong ally of the first vice president, was one of the most powerful figures in the current government.

Oil-rich South Sudan is struggling to increase production of crude oil several months after the signing of the peace deal.

Currently it pumps about 175,000 barrels per day of crude oil.