Abidjan - Riot police prevented an opposition demo from taking place in Ivory Coast's main city of Abidjan on Saturday by blocking off the rally site and threatening would-be demonstrators with teargas, opposition supporters said.One of the protest organisers was arrested, the opposition National Coalition for Change (CNC) told AFP.With a month to go until a presidential election in which President Alassane Ouattara is seeking a controversial second term, the CNC had called on supporters to gather in Abidjan's Yopougon neighbourhood.But protesters said they arrived early on Saturday morning to find the area occupied by heavily armed riot police."The slightest crowd was dispersed by teargas, activists were chased, it's unacceptable," said one young demonstrator.'Bullied and abused' Another opposition supporter, Jean-Jacques Djoro, said: "We were urged to take part in a rally. But police cordoned off the entire perimeter and prevented us from having our say a few weeks ahead of the elections."A group of around a dozen people selling goods near the protest site was dispersed by police, an AFP reporter saw. "Denis Ayeka, the person responsible for mobilising the CNC, was arrested," said Jean Enoc Bah, a founding member of the party."We condemn the police barbarianism," Bah said at a press conference. "Our friends were bullied and abused." The CNC appealed for a fresh protest on Monday to demand "fair access to state media" in the run up to the October 25 polls.The opposition coalition is demanding the dissolution of the electoral commission in charge of the election, which it considers to be favourable to the incumbent president.Ouattara is the favourite to win next month's polls, which are seen as crucial to restoring stability in the country after post-poll violence in 2010 and 2011 left more than 3 000 people dead.The unrest was triggered by former president Laurent Gbagbo's refusal to step down and acknowledge Ouattara's victory at the ballot box.In June, thousands of people demonstrated in Abidjan against Ouattara, with some saying he had done "nothing" for the country torn apart by years of political and military crisis.