* MDC says vote rigged through irregularities, intimidation
* Analysts doubt the MDC initiative will overturn result
* Legal challenge futile, says another defeated candidate
* Western governments have questioned vote's credibility (Adds details of MDC challenge, analyst, defeated contender)
By MacDonald Dzirutwe
HARARE, Aug 9 (Reuters) - Zimbabwe's Movement for Democratic Change (MDC) challenged President Robert Mugabe's landslide re-election in the top court on Friday, calling for a re-run of the July 31 vote it says was rigged.
Lawyers for the MDC, which is led by Mugabe's defeated rival Morgan Tsvangirai, filed papers with the Constitutional Court in Harare arguing the election should be annulled because of widespread alleged illegalities and intimidation of voters.
Western governments have questioned the vote's credibility.
"We want a fresh election within 60 days. The prayer that we also seek is to declare the election null and void," MDC spokesman Douglas Mwonzora told journalists outside the court.
Zimbabwe's electoral commission announced last weekend that Mugabe, Africa's oldest leader at 89, beat Tsvangirai with just over 61 percent of the votes against his rival's nearly 34 percent. The outcome extends for five more years Mugabe's 33-year rule in the southern African state once known as Rhodesia.
Zimbabwe's constitution says the court must rule on the case within 14 days. Analysts predict the MDC legal challenge is unlikely to prosper because they say Mugabe's ZANU-PF party dominates the judiciary and state institutions.
Mwonzora said the MDC was also preparing a legal challenge against the two-thirds majority in parliament won by ZANU-PF.
"Some High Court judges could back up MDC claims to seats in specific constituencies, but ZANU-PF's control of the Zimbabwe Electoral Commission and the Constitutional Court make any re-run very unlikely," Mark Rosenberg, senior Africa analyst for the Eurasia Group, wrote in a briefing note this week.
Another defeated presidential contender, Welshman Ncube, called the MDC challenge futile.
Tsvangirai was not present in court and the filing of the papers was a low-key event, with no public demonstration by MDC followers to back it. There was no visible police presence, but workers and soldiers peeped out through windows from the Zimbabwe Defence Forces headquarters across the road.
ZANU-PF has denied any vote-rigging in the election, which Tsvangirai, who had served as Mugabe's prime minister in a fractious unity government, has dismissed as a "huge fraud" and a "coup by ballot".
"The person on trial here is not the MDC but Mr. Mugabe. Zimbabweans expect nothing but justice," Mwonzora said.
Mugabe will be sworn in only after the case is decided.
While election observers from the African Union and the Southern African Development Community (SADC) broadly approved the presidential and parliamentary elections as orderly and free, the vote has been met with serious scepticism from the West.
The United States, which maintains sanctions against Mugabe, has said it does not believe his re-election was credible. The European Union, which has been looking at easing sanctions, has also expressed concerns over alleged serious flaws in the vote.
"DUPLICATED VOTERS NAMES"
In its arguments to the court seeking a re-run and detailing irregularities in the July 31 vote, the MDC alleged hundreds of thousands of voters were turned away, and that the voters' roll was flawed, containing at least 870,000 duplicated names.
In its assessment, Zimbabwe's leading domestic observers' body, the Zimbabwe Election Support Network (ZESN), had already called the election "seriously compromised", saying registration flaws may have disenfranchised up to a million people.
ZESN also cast doubt on the authenticity of the voters' roll, noting that 99.97 percent of voters in the countryside - Mugabe's main source of support - were registered, against just 67.94 percent in the mostly pro-Tsvangirai urban areas.
Ncube, leader of a smaller MDC faction who won only about three percent of the presidential vote, said he would not be bothering to challenge the election outcome.
He argued that the Constitutional Court had already shown its pro-Mugabe political colours when last month it rejected a bid to postpone the July 31 election date. Regional diplomatic grouping SADC had requested a postponement, arguing that this would allow more time to better prepare for a credible poll.
"The futility of going to the courts must be read with the Constitutional Court ruling, which led to the frog marching of Zimbabweans into an election for which ZEC (the Zimbabwe Electoral Commission) were ill prepared to run," Ncube said.
"Taking this matter to court will be akin to going to Robert Mugabe and asking him to reverse his 'victory'," Ncube said.
Mugabe, a former liberation fighter who has ruled Zimbabwe since he won 1980 elections that ended white minority rule, has rejected Western criticism of his re-election. (Additional reporting by Cris Chinaka; Writing by Stella Mapenzauswa and Pascal Fletcher; Editing by Pascal Fletcher and Michael Roddy)