South Africa's ruling African National Congress (ANC) said on Monday it had suspended the membership of former president Jacob Zuma after he announced he would vote for another party in this year's general election.

Zuma, whose nine years in office from 2009 were marked by corruption scandals and sluggish economic growth, said last month he would campaign for the new uMkhonto we Sizwe (MK) party in the vote, which is expected between May and August.

His suspension reflects deep-seated divisions in the party of liberation hero Nelson Mandela that has governed South Africa since the end of apartheid.

Analysts say this year's election could see the ANC lose its parliamentary majority for the first time since 1994, after its worst result to date in municipal elections in 2021.

"The formation of the MK party is not an accident," the ANC said in a statement. Forces were converging "to encourage rebel break-away groupings to erode the support base of the ANC," it added.

Zuma's suspension was necessary "to protect and preserve (the ANC's) integrity and prevent further damage to its reputation," the statement read.

There was no immediate comment from Zuma.

The MK party is named after the ANC's former armed wing, in a challenge to the long-dominant movement.

Zuma has been at odds with the ANC's leadership since he was forced to quit as party leader in 2018.

He has lashed out repeatedly against his successor, current President Cyril Ramaphosa, whose allies engineered Zuma's ouster.

Zuma retains a loyal following, especially in his home province of KwaZulu-Natal.

His jailing in 2021, for defying a court order to give evidence at a corruption inquiry, triggered protests, looting and unrest the left more than 300 people dead.