Sudan's President Omar al-Bashir launched his bid for re-election Sunday, facing little threat to his quarter century in power despite an ailing economy, multiple insurgencies and allegations of war crimes.

Bashir's supporters view him as a strong hand capable of holding the chaotic country together, while his opponents are hounded by the security forces, marginalised inside Sudan and riven by personal rivalries.

It is unclear whether anyone will challenge Bashir to lead the country of nearly 39 million people that covers an area almost one-fifth the size of the United States.

Formal applications to register for the April 13 vote opened Sunday, and the electoral commission said it had received Bashir's nomination.

The opposition looks set to boycott the vote, with Mariam al-Mahdi, deputy leader of the Umma Party, sharply criticising the move and saying her party would not take part in the April election.

"We believe it is a total waste not only of the time and resources of Sudan but also the hopes of the people," she told AFP by telephone.

The opposition also boycotted elections in 2010, the first contested vote since Bashir seized power in a 1989 coup.

In 2010, opposition leaders accused the president's loyalists of rigging ballots.

But Bashir has proven to be a political survivor.

Since 2009, the 71-year-old incumbent has defied an arrest warrant from the International Criminal Court for alleged war crimes in the nearly 12-year-old conflict in Sudan's western Darfur region.

In 2011, he oversaw a separation from South Sudan, after it voted to split following a 22-year civil war.

The president hinted last year he might not stand for re-election, raising fears of a succession struggle within his ruling National Congress Party, but in October, the NCP announced he would seek another term.

"Bashir is in a strong position internally within government," said Ahmed Soliman, Horn of Africa research assistant at Chatham House.

- Consolidating power -

He consolidated power earlier this month when parliament granted him the right to appoint state governors, who were previously elected.

Bashir has worked to shed his image as an international pariah, travelling to Egypt and Saudi Arabia last year and welcoming Russian Foreign Minister Sergei Lavrov to Sudan.

China's foreign minister also visited Khartoum on Sunday for talks about boosting relations and the conflict in neighbouring South Sudan.

The ICC's decision to shelve investigations into allegations of war crimes in Darfur over UN inaction gave him a further boost.

"The ICC's announcement that it was suspending its investigations was seen as a victory by President Bashir," said Jerome Tubiana, senior analyst for the International Crisis Group.

"The NCP should win without difficulty but all the problems will still be left," Tubiana added.

Sudan faces major economic challenges with nearly half of the country's population living in poverty, according to World Bank figures.

When South Sudan broke away, it took with it 75 percent of the formerly united country's oil production.

Insurgents are still battling government troops in Darfur as well as in Blue Nile and South Kordofan states on the South Sudan border.

Last January, Bashir announced a national dialogue to address the problems, inviting opposition groups, including rebels, to participate.

But the talks have yet to materialise, and critics view the invitations as a bid by Bashir to buy time before the elections.

- United opposition -

Opponents to Bashir's rule are more united than they have been for years but are still expected to struggle to challenge him.

In December, the Umma Party joined other opposition parties and civil society groups to sign the "Sudan Call" document demanding a transitional government to pave the way for free and fair elections.

Sudan's powerful National Intelligence and Security Service has kept up the pressure on opposition parties, arresting two signatories to Sudan Call.

NISS has also shown it will brook no dissent from protesters.

Its forces gunned down dozens of Sudanese who protested against the lifting of fuel subsidies in September 2013.

Their handling of the protests caused divisions within the NCP, with Bashir adviser Ghazi Salahuddin Atabani breaking away to form his own party.

But analysts say opposition failings have played into Bashir's hands.

"This alliance remains fragile because these opposition groups have for a long time been riven by personal rivalries," said Soliman of Chatham House.