Presidential hopefuls in Sudan, Africa's largest country, began campaigning yesterday for the first multi-party poll since 1986, with the nation wondering whether an end might be in sight to incumbent Omar al-Beshir's many years in power.

After being pushed back twice, the presidential election is set to take place on April 11, alongside legislative and regional polls.

Beshir, who seized power in 1989 with support from Islamists, is facing off against 11 other hopefuls, including the first woman ever to aspire to the presidency, and the two-time former prime minister he ousted.

The incumbent is also the world's first sitting president facing an international arrest warrant from the International Criminal Court on charges of alleged crimes against humanity in Sudan's western Darfur region.

The UN says up to 300,000 people have died and 2.7 million fled their homes since the ethnic minority rebels in Darfur first rose up against the Arab-dominated Khartoum government in February 2003.

Beshir's main challengers in the race are Yasser Arman, a secular Muslim from north Sudan representing the ex-rebel Sudan People's Liberation Movement, and Sadiq al-Mahdi, the premier Beshir ousted and who now leads the influential Islamist Umma Party.

Umma party dissident and presidential hopeful Mubarak al-Fadil told AFP he and Mahdi agreed yesterday to re-unite the party in a bid to bolster the opposition against Beshir.

"We have reached an agreement with Sadiq al-Mahdi to reunite the party.

"We will unite our political programme and our candidates," Fadil said. A spokesman for Mahdi confirmed the latest developments.

Fadil said however that he and Mahdi "did not yet discuss the question of who will be the presidential candidate" but observers believe Fadil will eventually quit the race in favour of Mahdi.

Mahdi, 74, is the historic head of the party and leader of the 'Ansar' Sufi brotherhood that venerates Muhammad Ahmad al-Mahdi who defeated British colonial forces under General Gordon in 1885.