A frontrunner in Democratic Republic of Congo's presidential elections said he had been barred from staging a rally in a key city on Tuesday, 12 days before polling day.Former oil executive Martin Fayulu, 62, a little-known lawmaker making a late surge in the campaign, said police had diverted him away from the rally venue in Lubumbashi, the country's second largest city."They made us follow an itinerary... (preventing us) from reaching the venue," he said in a tweet."They sent us to the home of 'Papa' Kyungu," he said, referring to a local opposition leader.An AFP reporter at the scene of the rally said police fired teargas to disperse several hundred people who had gathered to welcome Fayulu. The candidate himself accused the police of firing "live rounds."Earlier, Fayulu supporters were dispersed at Lubumbashi airport by teargas and jets of hot water, fired by police.Police said they had no information about any casualties but added that operations were still underway in late afternoon.Voters on December 23 will choose a successor to outgoing President Joseph Kabila, who has constitutionally remained in power as caretaker leader even though his second and final elected term ended nearly two years ago.At stake in the ballot is stewardship of mineral-rich country that has never known a peaceful transition of power since independence from Belgium in 1960.The 47-year-old has been in power since January 2001, taking the helm after his father, president Laurent-Desire Kabila, was assassinated.Twenty-one candidates are registered to vie to replace him. Fayulu last month was named the joint champion of several opposition parties. His main rivals are Felix Tshisekedi of the mainstream Union for Democracy and Social Progress opposition party, and Kabila's handpicked successor, Emmanuel Ramazani Shadary.One of Fayulu's supporters is Moise Katumbi, a former governor whose power base is Lubumbashi, but who has been barred from contesting the elections.The city, located in the southeastern province of Katanga, is also a Kabila stronghold. Shadary launched his elections campaign there on November 26.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.