Harare: Robert Mugabe resigned as Zimbabwe's president on Tuesday a week after the army and his former political allies moved against him, ending four decades of rule by a man who turned from independence hero to archetypal strongman.

The 93-year-old had clung on for a week after an army takeover and expulsion from his own ruling ZANU-PF party, but resigned shortly after parliament began an impeachment process seen as the only legal way to force him out.

Wild celebrations broke out at a joint sitting of parliament when Speaker Jacob Mudenda announced Mugabe's resignation and suspended the impeachment procedure.

People danced and car horns blared on the streets of Harare at news that the era of Mugabe -- who has led Zimbabwe since independence in 1980 -- was finally over.

Some held posters of army chief General Constantino Chiwenga and former vice president Emmerson Mnangagwa, whose sacking this month triggered the military takeover that forced Mugabe out.

"I am very happy with what has happened," said Maria Sabawu, a supporter of the opposition Movement for Democratic Change (MDC), outside the hotel where the impeachment process was happening.

"I have suffered a lot at the hands of Mugabe’s government," she said, showing her hand with a missing finger that she said she lost in violence during a presidential run-off election between Mugabe and opposition leader Morgan Tsvangirai in 2008.

Mugabe is the only leader Zimbabwe has known since a guerrilla struggle ended white-minority rule in the former Rhodesia.

During his reign, he took the once-rich country to economic ruin and kept his grip on power through repression of opponents, although he styled himself as the Grand Old Man of African politics and kept the admiration of many people across Africa.

Despite the outpouring of joy on the streets, Mugabe's downfall was as much the result of in-fighting among the political elite as a popular uprising, although thousands of people rallied against him in the days after the army intervened last week.

DECADES OF ISOLATION

The army seized power after Mugabe sacked Mnangagwa, ZANU-PF's favourite to succeed him, to smooth a path to the presidency for his wife Grace, 52, known to her critics as "Gucci Grace" for her reputed fondness for luxury shopping.

Mugabe's refusal to resign prompted the impeachment procedure. His resignation letter, read out by the parliamentary speaker, did not indicate any preferred successor. Speaker Mudenda said he was working on legal issues to make sure a new leader was in place by the end of Wednesday.

Mnangagwa, the former vice president whose whereabouts are unknown after fleeing the country in fear for his safety, is seen as the most likely to take over.

A former security chief known as The Crocodile, he was a chief lieutenant to Mugabe for decades and stands accused of participating in repression against Zimbabweans who challenged the leader.

Reuters reported in September that Mnangagwa was plotting to succeed Mugabe, with army backing, at the helm of a broad coalition.

The plot posited an interim unity government with international blessing to allow for Zimbabwe's re-engagement with the world after decades of isolation from global lenders and donors.

Theresa May, prime minister of former colonial power Britain, said Mugabe's resignation "provides Zimbabwe with an opportunity to forge a new path free of the oppression that characterised his rule" and that Britain, as "Zimbabwe’s oldest friend", would do all it could to support the country.

Mugabe led Zimbabwe's liberation war and is hailed as one of post-colonial Africa's founding fathers and a staunch supporter of the drive to free neighbouring South Africa from apartheid in 1994.

But many say he has damaged Zimbabwe's economy, democracy and judiciary by staying in power for too long and has used violence to crush perceived political opponents. The country faces a foreign exchange payments crisis and roaring inflation.

Since the crisis began, Mugabe has been mainly confined to his "Blue Roof" mansion in the capital where Grace is also believed to be.

Amnesty International said Zimbabwe must renounce the abuses of the past and embrace the rule of law.

Under three decades of violent repression, tens of thousands of people were tortured, forcibly disappeared or killed under a culture of impunity that allowed "grotesque crimes to thrive," the human rights group said.

“The people of Zimbabwe deserve better. The next generation of leaders must commit itself to upholding the constitution, living up to Zimbabwe’s international human rights obligations and treating its people with dignity and justice,” Amnesty said in a statement.