A candidate in Congo Republic's presidential election has claimed that the poll was an "electoral coup" marred by vote-rigging and called on the courts to annul the result. Provisional results on Tuesday showed that President Denis Sassou Nguesso was re-elected with more than 88% of Sunday's vote, extending his 36-year rule in the Central African country. Mathias Dzon, who came third, said he will file an appeal with the constitutional court on Thursday asking that the election be annulled. He did not provide proof of fraud. Spokespeople for the government, the electoral commission and the constitutional court did not respond…