President Ouattara brandished a promise to win on the first ballot -- but opponents say his standing again is unconstitutional

Sporadic violence flared in Ivory Coast on Saturday after President Alassane Ouattara was chosen by his ruling party to run for a third term in an October election, despite furious opposition charges the move is unconstitutional.

Ouattara, in power since 2010, said in March he would not stand again but changed his mind after the death of prime minister Amadou Gon Coulibaly -- seen as his anointed successor -- of a heart attack in July.

After his official nomination on Saturday, Ouattara vowed to score a first-round knockout victory before tens of thousands of supporters at an Abidjan rally.

"Going back on my decision was not easy," said Ouattara, who insisted: "There is nothing preventing me from standing."

"I did not have the right to place my personal project above the urgent situation in which the country finds itself," he said.

But his party's decision provoked outrage among young opposition supporters who took to the streets to voice loud and violent protest in several major cities. 

The constitution limits presidents to two terms, but 78-year-old Ouattara and his supporters argue that a 2016 constitutional tweak reset the clock, allowing him to seek a third.

Opposition and civil society groups say his standing again amounts to a "coup" that risks triggering chaos in the world's biggest cocoa producer.

'No third term'

Violence erupted in several towns, notably Divo, a cocoa-growing centre 200 kilometres (125 miles) northwest of Abidjan where pro-opposition youths clashed with young supporters of the ruling party.

"There are people wounded. The small bus station, bars and shops have been set on fire and looted," Davo's political representative Famoussa Coulibay told AFP.

"There have been police reinforcements. We will try to calm things down with the leaders of the community," Coulibay added.

Gagnoa, the home town of former president Laurent Gbagbo further to the northwest, also saw unrest.

"Young people close to the opposition burned tyres and set up barricades in different parts of town," one resident told AFP, adding that protesters shouted "we don't want a third mandate."

There were further incidents in the southwest at Bonoua, the hometown of former first lady Simone Gbagbo, which also saw unrest Friday.

Coaches, the central market and about 30 shops were set ablaze, according to resident Georges Vangah.

After Ouattara's re-election announcement earlier this month, mass protests descended into three days of violence in which six people died and a hundred were injured.

His ruling Houphouetist Rally for Democracy and Peace (RHDP) party nominated Ouattara as its candidate at the rally.

"We remain focused on the election, with a record to defend and a project to propose to Ivorians," party spokesman Mamadou Toure told AFP, branding the street demonstrations against Ouattara's candidacy a "dismal failure".

Rival candidates rejected

The government Thursday announced a ban on all outdoor protests until September 13 in the wake of the deadly demonstrations this month.

Outtara's change of heart has heightened tensions before the October 31 vote.

Ivory Coast is still traumatised by a brief civil war that erupted after 2010's election, when then president Gbagbo refused to cede to the victor, Ouattara.

On Friday, election authorities rejected appeals by Gbagbo and former rebel leader Guillaume Soro to be allowed to run in October.

The two men had appealed to the Independent Electoral Commission (CEI) against a decision to not include them in electoral lists for the ballot.

Gbagbo was freed conditionally by the International Criminal Court in The Hague after he was cleared last year of crimes against humanity over the 2010 election unrest.

His return to Ivory Coast would be sensitive before the presidential election. His Ivorian Popular Front (FPI) party urged him to throw his hat in the electoral ring.

Soro, a former rebel leader, has been forced into self-imposed exile in France in the face of a long list of legal problems at home.

He was a leader in a 2002 revolt that sliced the former French colony into the rebel-held north and the government-controlled south and triggered years of unrest.

Soro was once an ally of Ouattara, helping him to power during the post-election crisis in 2010, but the two eventually fell out.