Mugabe, 83 and in power since Zimbabwe's independence from Britain in 1980, is seeking re-election in presidential and parliamentary elections set for March 2008 after some senior officials in his ZANU-PF party failed to stop him from running.

Mugabe, who looks fit for his age and remains combative in the face of a crumbling economy and growing discontent -- has mobilised his independence war veterans, his shock political troops, to assert his authority.

Thousands of ZANU-PF supporters -- ferried into the capital Harare by bus and train -- converged at various points in the city on Friday, singing revolutionary songs and pledging support for one of the world's most controversial leaders.

Men and women, both young and old, jogged around as they prepared to march for miles to Zimbabwe Grounds -- a sprawling sports arena in Harare's Highfield township -- where Mugabe was due to address them later in the day.

Although Mugabe has managed to ride out the storm in the last seven years, analysts say he faces a potent threat from the economy -- seen by the World Bank as the fastest shrinking outside a war zone -- because it may spark social unrest.

Opponents allege Mugabe, a master of political intrigue, has seen off challenges through tough policing, vote-rigging and patronage to reward supporters. He denies the accusations.

Mugabe's record of punishing ZANU-PF officials who cross him has left party members more reluctant than ever to speak publicly about the party's internal debates, analysts say.

But some ZANU-PF officials quietly say the economy and their business interests suffered under Mugabe's leadership and want him to step aside and appoint a successor capable of reviving the economy and improving strained ties with key Western donors.

War veterans leader Jabulani Sibanda told state media that the "one million men and women march" was meant to demonstrate that Mugabe, who co-led Zimbabwe's independence war in the 1970s, enjoyed solid support despite Western powers' opposition to his rule.

"Comrade Mugabe is our leader, and we are prepared to wage another war to defend his leadership and our sovereign right to choose our own revolutionary leader," he said.

The economy has all but collapsed since Mugabe ordered the seizure of white-owned farms to give to landless blacks in 2000, gutting the key commercial agriculture sector.

Zimbabwe has suffered a wave of sporadic labour strikes over pay, forcing Mugabe to print money to keep his grip on the economy, analysts say.