HARARE-- Emmerson Mnangagwa has urged Zimbabwe to unite behind his presidency, while taking the oath of office following a divisive election.

The Constitutional Court confirmed Mnangagwa as President on Friday, dismissing a challenge by the man he beat in the July 30 ballot, Nelson Chamisa.

Thousands of Zimbabweans, some bussed in, and foreign leaders including South Africa's Cyril Ramaphosa and Paul Kagame of Rwanda gathered at Harare's national stadium for Sunday's swearing in.

"I exhort us to commit ourselves collectively to develop our motherland what unites us is greater than what could ever divide us," Mnangagwa said in his inauguration speech.

He also reaffirmed pre-election pledges to revive Zimbabwe's crippled economy and settle outstanding debts with foreign lenders, and reiterated he would call an independent inquiry into a "regrettable and unacceptable" army crackdown following the vote in which six people died.

"Now is the time for us all to unite as a nation and grow our economy," Mnangagwa said.

He took the oath before Chief Justice Luke Malaba who, together with eight other judges, had ruled on Friday against Opposition Leader Chamisa's petition.

In the election, Mnangagwa just reached the threshold of 50 per cent of votes that he needed to avoid a runoff.

The ballot was touted as a crucial step towards shedding the pariah reputation Zimbabwe gained under Mnangagwa's predecessor Robert Mugabe, and securing international donor funding.

The election was marred by procedural lapses and followed by the crackdown against opposition supporters, which recalled the heavy-handed security tactics that marked Mugabe's 37-year rule.

Mugabe, who has accused Mnangagwa � his former head of intelligence and defence minister � of betrayal, did not attend Sunday's ceremony, though the 94-year-old former leader's daughter Bona did.

In keeping with an earlier promise, Chamisa also stayed away.