Security forces firing tear gas and sten grenades clashed with stone-throwing protesters in Ivory Coast on Thursday, with at least three people shot dead as a tense political showdown turned violent between supporters of the two men claiming the nation’s presidency.

An Associated Press reporter in Abidjan’s downtrodden Abobo neighbourhood saw the bodies of three men laying in the street. One had been shot in the head, two others in the chest. Several more were wounded during midmorning clashes elsewhere, according to AP journalists on the scene.

Sporadic bursts of gunfire were audible across the city. The violence brought skyscraper-lined Abidjan to a standstill. Businesses were closed and fearful residents stayed home. City streets were deserted except for soldiers and police.

Longtime opposition leader Alassane Ouattara - whose election victory has been acknowledged by the U.N., U.S., France and the African Union - has called on his backers to help him take control of state institutions. They have vowed to march to the national television station on Thursday to install a new state television chief.

The two stations broadcast from the building are the only Ivorian broadcasters in the country. They provide a powerful voice for the person controlling them: In the days after the U.N. said incumbent Laurent Gbagbo lost, people watching Gbagbo-controlled state TV saw only the announcement of his victory.

The TV building is being heavily protected by Mr. Gbagbo’s troops, and violent confrontation is likely if the two sides meet. On Thursday, police and soldiers guarded the building, sealing off streets around it and blocking them with makeshift roadblocks made of wooden tables and benches. Two armoured personnel carriers filled with helmeted troops was parked nearby.

Across Abidjan, soldiers and police stood guard at nearly every major intersection. Violence broke out in several parts of the city as security forces tried to prevent crowds from gathering.

In the Treichville neighborhood, riot police and soldiers loyal to Mr. Gbagbo fired tear gas to disperse one group of around 500 people. Streets filled with hazy clouds of smoke as gas canisters burned. Similar violence broke out in the city’s Koumassi district, as well as Abobo, where police fired several stun grenades to break up a demonstration by 500 to 1,000 Ouattara militants.

“The risk for yet more bloodshed and senseless loss of life ... is extremely high,” said Corinne Dufka, a senior researcher for Human Rights Watch based in Dakar, Senegal. “All those concerned must do all they can to prevent this scenario - soldiers and police must be given explicit orders to use restraint and minimum use of force; and the U.N. must stand ready to fulfill their mandate to protect those being threatened with violence.”

On Wednesday, U.N. Secretary-General Ban Ki-moon warned the politically charged environment could spark a new civil war. A long-delayed presidential election was held recently to unite the country and begin a new era, but the top-two finishers both claim the presidency and the vote has fuelled profound fears of new unrest.

U.N. spokesman Martin Nesirky said Mr. Ban is “deeply concerned” about the electoral stalemate in the West African nation and warned violence at this time “could have unpredictable consequences, including re-igniting civil war.”

Mr. Ouattara also plans a second march on Friday to take back other government buildings and hold a Cabinet meeting. For now, he governs from a hotel guarded by supporters and U.N. troops.

“The next two days will determine everything. It’s all or nothing,” said Jean—Claude N’dri, a cable television salesman in Treichville. “They’re just using tear gas now,” he said of the police, “but if this continues they’ll shoot with live rounds, we’re sure of it.”

In a message read on state television Wednesday, the Gbagbo-backed army warned Mr. Ouattara’s supporters not to participate in Thursday’s march. Military spokesman Hilaire Gouhourou claimed the army had proof that the U.N. peacekeeping mission supported it, and said the army would hold U.N. envoy Choi Young-jin responsible should violence occur.

People should “abstain from such a perilous undertaking,” Mr. Gouhourou warned.

Ivory Coast has been operating with two presidents and two governments since a disputed November 28 runoff. Mr. Ouattara was declared the winner by the country’s electoral commission, but the next day, the constitutional council overturned those results after invalidating a half-million votes from Mr. Ouattara strongholds.

The dispute has raised fears of renewed unrest in the world’s largest cocoa producer, which is struggling to recover from the 2002-2003 civil war that divided the country in two. Mr. Ouattara draws much of his support from the country’s rebel-held north, while Mr. Gbagbo’s power base is in the south.

While Mr. Ouattara’s victory has been recognized by numerous foreign governments, Mr. Gbagbo maintains control of state media and the army, and continues to occupy the presidential palace and government buildings. He has kept the country under a nightly curfew since before the election, and extended it an additional week on Monday.

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