Jean-Pierre Bemba, an opposition leader and former rebel leader in the Democratic Republic of Congo (DRC), has officially launched his bid for the country's presidency, putting forward his candidacy for the long-delayed election in December.

The move by Bemba on Thursday came a day after he arrived home after 11 years in exile and prison.

He lodged his documents at the electoral commission offices in the capital, Kinshasa, throwing down the gauntlet to his rival President Joseph Kabila, who has ruled for 17 years.

"I can confirm that I indeed had a voting card and I filed all the papers," Bemba said outside the electoral commission headquarters.

"Now it is up to the CENI [the national election board] to handle all the applications. For me, I have submitted the entire file, it is in order," added the 55-year-old, also a former DRC vice president.

Bemba was accompanied by his wife and members of the Movement for the Liberation of the Congo (MLC), a former rebel group-turned-political party that he founded.

The International Criminal Court (ICC) in The Hague acquitted Bemba of war-crimes charges in June.

Upon returning to the DRC on Wednesday, Bemba was greeted by thousands of enthusiastic supporters, many of whom chanted anti-Kabila slogans.

A heavy contingent of police escorted the convoy of Bemba, who was not allowed to make any stops to address the large crowds who lined the streets of Kinshasa.

"I'm happy because Bemba has been vindicated by the same court that convicted him. Now he is here and we are just glad to see him," one of his supporters told Al Jazeera.

"We are suffering in this country. Children are not going to school, things are not moving. His return gives up hope," said another.

According to observers, Bemba's return has introduced even more uncertainty into an already volatile election process.

Kabila was scheduled to stand down at the end of 2016 after his second elected term, technically the last permitted under the constitution. But he has stayed in office, invoking a constitutional clause enabling him to remain in power until a successor is elected.

His time in charge has been widely criticised for rights abuses, corruption and incompetence.

Bemba lost presidential elections to Kabila in 2006 and was later accused of treason when his bodyguards clashed with the army in Kinshasa.

In 2007, he fled to Belgium, where he had spent part of his youth.

He was then arrested in Europe on a warrant by the ICC for war crimes committed by his private army in the neighbouring Central African Republic between 2002-03, when its then president, Ange-Felix Patasse, sought his help to repel a coup attempt.

He was sentenced in The Hague in 2016 to 18 years before the conviction was overturned in June on appeal.

The ICC declared Bemba could not be held responsible for crimes committed by his troops.

The court is due to issue a ruling in a separate case, in which Bemba was sentenced to jail and fined 300,000 euro ($350,000) in 2017 for bribing witnesses during his main trial.

But legal experts expect him to be released definitively if time spent behind bars is taken into account.

Still, Bemba faces some hurdles in his bid for presidency, said Al Jazeera's Catherine Soi, reporting from Kinshasa.

"The law says a candidate has to be in the country for at least a year before contesting an election. The fact that Bemba has been away for more than 10 years and still has a pending witness-tampering case at the ICC could harm his chances," she said.

The DRC has never known a peaceful transition of power since it gained independence from Belgium in 1960 - and some experts fear the current crisis may spiral into bloodshed.

Two wars unfolded from 1996-97 and from 1998-2003 that sucked in other countries in central and southern Africa.

Smaller, but still bloody, conflicts dog the centre and east of the vast country today.