South Africa's ruling African National Congress (ANC) has formally asked President Jacob Zuma to resign, a senior party official has confirmed.

The decision to "recall" him "urgently" followed marathon talks of the ANC's top leadership body.

Mr Zuma, 75, agreed to step down, but only in the next three to six months, the official added.

Mr Zuma, who has been in power since 2009, has been dogged by corruption allegations.

But he has resisted increasing pressure to quit since December, when Cyril Ramaphosa replaced him as leader of the ANC.

Ace Magashule, the ANC's secretary-general, told reporters the ANC's National Executive Committee (NEC) decided the removal should be "treated with urgency".

"It is obvious we want Comrade Ramaphosa to come in as the president of South Africa," he added.

Despite Mr Magashule telling reporters "the decision is now final", he revealed Mr Zuma told him that he "did not believe the NEC has the right" to make such a ruling.

He said the president was expected to respond to the NEC's decision on Wednesday, although they had given him no deadline.

What has Mr Zuma done wrong?

Mr Zuma's presidency has been overshadowed by allegations of corruption which he has always vehemently denied.

In 2016, South Africa's highest court ruled that Mr Zuma had violated the constitution when he failed to repay government money spent on his private home.

Last year the Supreme Court of Appeal ruled that he must face 18 counts of corruption, fraud, racketeering and money-laundering relating to a 1999 arms deal.

More recently, Mr Zuma's links to the wealthy India-born Gupta family, who are alleged to have influenced the government, have caused his popularity to plummet.

Both Mr Zuma and the Guptas deny the allegations.

How likely is Mr Zuma to quit?

Correspondents say it will be very difficult for him to resist a formal request to resign but he would not be legally obliged to do so and could technically carry on as president despite losing the faith of his party.

However, he would then be expected to face a confidence vote in parliament. This has been scheduled for 22 February, but it could be held earlier.

Mr Zuma has survived other such votes but he is not expected to pull it off again. A confidence vote would be considered a humiliating process for him and the party.

South African media are calling President Zuma's seemingly inevitable exit "Zexit".

His predecessor, Thabo Mbeki, resigned in 2008, also after a power struggle with his deputy.

The deputy in question was Jacob Zuma, who took over the presidency the following year.

Why is this happening now?

The ANC was badly rattled by its performance at the 2016 local elections when it won its lowest share of the vote since coming to power under the late Nelson Mandela in 1994.

It wants to project a fresh image for next year's general election. Having served two terms in office (South African presidents are elected by parliament), Mr Zuma cannot legally return to power in any case.

On Monday, opposition parties called for an early election.

"Anyone from the ANC that wants to lead this country, must get their mandate from the people of South Africa," Democratic Alliance leader Mmusi Maimane told reporters.