KHARTOUM – Sudanese President Omar al-Beshir on Thursday promised the country's first multi-party elections in over two decades will be 'free and fair', as campaigning for the April 11-13 vote winds down.

"The elections will be fair and free and clean and exemplary," Beshir told a large gathering at the site of a massive hydroelectric plant in northern Sudan, marking the project's final phase.

They will be clean, because "elections are a religious duty," the Islamist-leaning leader said at the event, which was broadcast on state television.

Sudan will hold its first multi-party vote since 1986 on Sunday, which will include presidential, legislative and local elections.

The Sudanese leader, who focused his campaign on economic development and has taken his rallies across the country, chose to wrap up at the site of his flagship project, the Chinese-engineered Merowe Dam.

"All our projects... are a religious duty," Beshir told the gathering.

The dam's inauguration on March 3, 2009, came on the eve of announcement by the International Criminal Court of the issue an arrest warrant against the Sudanese leader for war crimes and crimes against humanity in the western region of Darfur.

The 66-year-old leader, who has led Africa's largest country since 1989, has been scrambling to maintain credibility after a boycott by opposition parties.

During Thursday's brief speech, Beshir made no mention of the boycott.

The Umma party, one of the two largest opposition groupings in the country, announced late on Wednesday its boycott of the election at all levels.

Umma was among a group of opposition parties that had given the Sudanese government four days from April 2 to implement key reforms in return for a pledge to take part in elections that would be pushed back to May.

But on Tuesday, the national elections commission had insisted that the vote would go ahead as planned from Sunday till Tuesday.

"The political bureau discussed the issue over the past two days... In the end, we came to the conclusion that our conditions for postponing the elections had not been accepted," said Sarah Nugdalla, a senior member of the Umma's politburo.

The Umma announcement came just hours after the European Union said it was pulling its election monitors out of Darfur, citing insecurity.

The former southern rebel Sudan People's Liberation Movement had already decided to boycott the election in northern Sudan, after withdrawing their presidential candidate Yasser Arman from the race.

The SPLM said however it would still field candidates in the sensitive border states of Blue Nile and South Kordofan, where the party enjoys support.

With the withdrawal of both Beshir's key challengers --Arman and Umma's Sadiq al-Mahdi-- little suspense remains in the race and Beshir looks to secure a comfortable win.

The election is seen as a prelude to a crucial referendum on southern independence scheduled for 2011.

North and south Sudan were engaged in a bitter decades-long civil war that left around two million dead and some four million displaced.

The two parties signed the Comprehensive Peace Agreement in 2005, which provided for both the elections and the referendum.

Copyright © 2010 AFP. All rights reserved.