BOGOTA (Reuters) - Heavy fighting raged between elite counterinsurgency troops and Marxist rebels in the jungles of southern Colombia on Tuesday, the army said, amid reports that dozens of soldiers had been killed. Army commander-in-chief Gen. Mario Hugo Galan said only that an "indeterminate number" of soldiers had died in "intense combats" that first flared over the weekend along the banks of the River Caguan in Caqueta province. Defense Ministry sources said at least nine soldiers had died and 12 others were injured, but added that the final toll "could be much higher." A spokesman said the army had sent a fleet of aging Vietnam-era fighter-bombers to give air support to the counterinsurgency unit, said to number about 120 men. President Ernesto Samper called an emergency security council meeting with key cabinet ministers and army leaders late on Tuesday. "Certainly people will lose their lives in these combats. It is not easy to get information about what is happening in this jungle region and bad weather has prevented us flying helicopters in," a stony-faced Defense Minister Gilberto Echeverri told reporters after the crisis talks. The fighting has been taking place about one hour downriver from the town of Cartagena del Chaira - one of the power bases of the FARC`s Southern Bloc. The FARC`s 15th Front, led by Commander Fabian, is known to have been massing guerrilla fighters in that area for the last month. The fighting came less than a week before the Mar. 8 congressional elections. The armed forces high command said early on Tuesday that the military had been placed on maximum alert in a bid to stem a nationwide guerrilla campaign to sabotage the ballot. The rebels have described the upcoming legislative elections as a "festival of snake handlers promising miracle cures." They have kidnapped 10 mayors across Colombia in the last week and have ordered another 21 to step down, in a bid to frighten voters.