South Africa's Cyril Ramaphosa is to be sworn in for a new term as president at a ceremony in Pretoria on Wednesday, after his weakened African National Congress (ANC) struck a government coalition deal.

Lawmakers voted overwhelmingly to re-elect the 71-year-old last week, after a May 29 general election that produced no outright winner.

He will be officially inaugurated for a new five-year term before MPs, foreign dignitaries, religious and traditional leaders and others at the Union Buildings, the seat of government.

The presidency said at least 18 heads of state and government, many from other African countries are to attend.

It shared photos of some -- including Nigerian President Bola Ahmed Tinubu, Angola's Joao Lourenco, Congo Brazzaville's Denis Sassou Nguesso and Eswatini's absolute leader King Mswati III -- landing at a military base outside the capital.

China, Egypt, Cuba, Zimbabwe and the State of Palestine are among those that "will be represented at a high level", the presidency said.

The ceremony includes a 21-gun salute and a fly past by the air force.

Ramaphosa will be sworn in by the head of the constitutional court, Chief Justice Raymond Zondo, and then deliver an inaugural address.

Guests in suits, fancy dresses and coats to keep warm in the chilly winter weather started to arrive early in the morning amid a heavy police presence.

VIPs, some singing anti-apartheid struggle songs, were allowed into a small amphitheatre within the imposing, sandstone government building.

Other attendees, some holding South African flags, sat on a lawn outside as dancers and musicians performed on a big stage.

- Third time lucky -

It will be the third time Ramaphosa takes the oath.

The former trade unionist turned millionaire businessman first came to power in 2018, after his predecessor and rival Jacob Zuma was forced out before the end of his term under the cloud of corruption allegations.

Ramaphosa was then re-appointed for a full five-year term in 2019. In South Africa, voters elect the parliament which then votes for the president.

Ramaphosa promised a new dawn for South Africa, launched an anti-graft drive and started to reform a collapsing energy system.

But under his watch, the economy languished, blighted by power cuts, crime remained rife and unemployment increased to 32.9 percent.

In May, he led the ANC into yet another vote, but the historied party of the late Nelson Mandela came out bruised.

It won only 40 percent of the vote -- down from 57.5 percent five years earlier.

For the first time since the advent of democracy in 1994, it lost its absolute majority in parliament and was left scrambling to find coalition partners to remain in power.

It has since agreed to form what it calls a national unity government with several other parties.

They include the centre-right Democratic Alliance (DA), the Zulu nationalist Inkatha Freedom Party, the anti-immigration Patriotic Alliance and the small centre-left GOOD party.

The deal allowed Ramaphosa to comfortably see off a last-minute challenge by firebrand leftist politician Julius Malema, with 283 lawmakers in the 400-seat National Assembly voting to put him back in office.

But it has faced a vociferous opposition from the left, with Malema's Economic Freedom Fighters and former president Zuma's uMkhonto weSizwe (MK) refusing to take part and denouncing the inclusion of right-wing parties and the white-led, free-market DA.

MK came third in the election but has contested the results.

Party spokesman Nhlamulo Ndhlela said in a statement that its lawmakers would snub the "farcical inauguration of Cyril Ramaphosa as the puppet DA-sponsored President", also using a racial slur to describe the ANC leader.

Ramaphosa is expected to announce his cabinet within days of his inauguration, as talks with coalition members continue.