A long time rebel General, also South Sudanese military commander Peter Gatdet Yak, has died in Sudan, opposition officials said on Tuesday.

“We have lost General Peter Gatdet, it is a great loss to the nation,” South Sudanese opposition official Mahjoub Biel told Radio Tamazuj. “He was undergoing treatment in Khartoum. He died of a heart attack,” he added.

General Gatdet died at Yastabshiron Hospital in Khartoum on Monday, said Mahjoub.

Several family members confirmed the death, but declined to give further details, Radio Tamauj, said.

The opposition group Sudan People’s Liberation Movement-In-Opposition (SPLM-IO) led by Riek Machar has issued a condolence message extending condolence to Gatdet’s family.

Reports have it that Mr Gatdet switched sides several times during the north-south civil war that killed hundreds of thousands of people.

Gatdet, from Mayom County in South Sudan's oil-rich Unity region, was leading a rebel group calling itself South Sudan United Movement (SSUM).

He also led a faction of opposition umbrella, which split into two groups over leadership disagreements last year.

After the civil war broke out in December 2013, General Gatdet joined the rebel group led by former vice president Riek Machar but he broke away later and formed his SSUM group.

Gatdet was part of the 2018 peace deal that calls on rival factions to unify their forces into a national army before the formation of a unity government in May.

No official announcement has been made as to who succeeds him within the SSUM movement.