By Daniel Wallis and Diego Ore CARACAS (Reuters) - Rival supporters in Venezuela's presidential election fought and threw stones on Wednesday before a campaign stop by opposition leader Henrique Capriles less than a month before the October 7 vote. Both sides blamed each other for the worst flare-up since the campaign began in July. Several people were hurt as dozens clashed around an airport in Puerto Cabello - even chasing each other across the runway - where Capriles had been due to land. One pickup truck carrying opposition campaign materials was set on fire, and at least one other car was smashed up. There have already been a handful of clashes on the campaign trail as Capriles tries to unseat President Hugo Chavez and end 14 years of the socialist leader's self-styled revolution. These acts are not spontaneous. There is someone responsible," Capriles, the 40-year-old governor of Miranda state, told a rally after the clashes, blaming the president personally. The election has so far generated much less violence than some locals had feared. But there is a huge number of guns in public hands, and with tempers becoming frayed as voting day nears there remains the risk of a more serious confrontation. State media said more than 20 people had been hurt, while an opposition TV network gave a lower number of wounded. Chavez's supporters blamed the opposition for the clash in Puerto Cabello, which closed the main road to the airport and forced Capriles to arrive in the area by a small boat instead. Puerto Cabello is 60 miles west of Caracas in central Carabobo state. Puerto Cabello's mayor is a "Chavista," but the governor of the state is an opposition supporter. The head of Chavez's campaign team told a weekly news conference in the capital that it had photographs of members of the Carabobo state police "lashing out" at Chavez supporters during the clashes. But he did not show the pictures to reporters. Chavez did not mention the disturbance during a two-hour televised speech to a campaign event in the evening with members of a social development project called "Mothers of the Slum." The 58-year-old leads the majority of Venezuela's best-known opinion polls, but they are notoriously controversial and divergent in the country of 29 million people, and one major pollster puts Capriles ahead. Among the myriad local polling companies, respected Datanalisis had Chavez ahead by 12 points in July, though Capriles' numbers have been creeping up and another well-known pollster, Consultores 21, has them neck-and-neck. Both sides discount unfavorable polls and say their candidate is ahead. The president remains hugely popular with many of Venezuela's poor majority, partly due to generous oil-funded welfare projects such as subsidized food stores, and because of his own humble roots and folksy charisma. He frequently accuses opposition leaders of planning to scrap his social "missions" if they win power. Capriles rejects that, saying he will launch new missions, keep the current ones and improve those which he says do not work. United Nations data support the government's line that poverty has been reduced under Chavez, but the opposition says he should have achieved much more given the huge oil revenue his administration has received since he took office in 1999. Additional reporting by Mario Naranjo, Eyanir Chinea and Hugh Bronstein; editing by Philip Barbara