HARARE — Africa's oldest ruler Zimbabwe President Robert Mugabe hit out at "vile" Western critics as he was sworn in for another five-year term Thursday in a stadium packed with jubilant supporters.

Festooned in a sash, garland and medals, the 89-year-old dismissed accusations the July 31 election that returned him to power was rigged and vowed to rejuvenate the foreign-dominated banking and mining sectors.

The ceremony was boycotted by opposition leader and former prime minister Morgan Tsvangirai, who condemned the election as "a farce" and "a massive fraud" and demanded a forensic audit of the results.

Mugabe lambasted Western countries, which have also questioned the legitimacy of his election victory.

"We dismiss them as the vile ones whose moral turpitude we must mourn," he said, venting against Britain, Australia, Canada and the United States.

Unlike previous low-key investitures, Thursday's event -- replete with banners, flags and chants -- carried strong echoes of Mugabe's inauguration as prime minister of a newly independent Zimbabwe in 1980.

A no-show by many leaders from neighbouring countries -- including President Jacob Zuma of regional power-broker South Africa -- did little to dampen enthusiasm.

"I promise you better conditions," he told the 60,000 capacity crowd of supporters at a stadium in Harare.

"The mining sector will be the centrepiece of our economic recovery and growth. It should generate growth spurts across the sector, reignite that economic miracle which must now happen."

The inauguration had been delayed after Tsvangirai challenged the poll results in a petition to the Constitutional Court that was later withdrawn.

Mugabe's 33-year rule since Zimbabwe's independence has been marked by a drive to transfer foreign-owned and white-owned assets, including farms, to blacks.

His inner circle has faced decades of international sanctions over rights abuses, and the leader said he expected the punitive measures to continue.

"Most likely we shall remain under these sanctions for much longer."

"We continue to look East," Mugabe said about the search for investors.

Former colonial power Britain called Thursday for an "independent investigation" into the conduct of the election, which Mugabe officially won by a landslide.

The July 31 polls were his fourth victory, but his opponents also denounced rigging in elections in 2002 and 2008, which were marred by widespread violence against his opposition supporters.

On Thursday, gates to the Chinese-built stadium, the venue of Mugabe's inauguration as president in 1987, opened shortly after dawn.

Mugabe was greeted in the stadium by thunderous cheers and whistling. On board a military truck he inspected assembled military personnel.

The day was declared a public holiday, helping boost attendance.

"Mr. Mugabe, you are one of a kind,"sang a group of supporters slamming the sides of the minibus taking them to the stadium, while others waved fists as drivers honked their horns.

A concert will include artists from South Africa, Zambia and Jamaica -- whose iconic singer Bob Marley played at Zimbabwe's independence event.

Banners around the oval stadium carried messages praising African leaders and denouncing Western governments accused of meddling in Zimbabwe's political affairs.

"Which African ever observed elections in Europe, America?" read one banner. "Africa has spoken, respect its voice," said another.

-- 'Farewell event for Mugabe' --

Eldred Masunungure, a political scientist from the University of Zimbabwe, said the event was at once Mugabe's victory lap and his "last supper."

"This inauguration is being projected as the crowning of a victory of a struggle for the past 13 years against big Western powers," he said.

There is however also an "unintended meaning," he said. "It can be read as a farewell event for Mugabe. It reminds one of Jesus's Last Supper."

The vote ended a shaky power-sharing government Mugabe and Tsvangirai formed four years ago to avoid a tip into all-out conflict following a bloody presidential run-off election.

This time round the electoral commission declared Mugabe the winner with 61 percent of the vote, against 34 percent for Tsvangirai.

The Constitutional Court confirmed Mugabe as president and declared the elections "free, fair and credible," saying the results "reflected the free will of the people of Zimbabwe."

But among a series of complaints, local observers and Tsvangirai queried the suspiciously high number of voters who were turned away from polling stations in urban areas, which are considered opposition strongholds.

Tsvangirai also charged that his supporters in rural areas were intimidated by Mugabe party backers into feigning illiteracy and voting in the presence of police and election officers.

But regional grouping the Southern African Development Community and the African Union were less critical.