New Delhi/Raipur, April 4 The ambush that left 22 security personnel dead was led by some 400 Maoists who surrounded the jawans from three sides in an area devoid of vegetation and rained bullets from light machine guns (LMGs) and also used IEDs to mount the attack that went on till evening, officials said. The Maoists carried their dead, estimated to be about 10-12, on tractor-trailers and also decamped with some sophisticated arms. Officials said inputs were received that Naxals were conducting a counter-offensive exercise in the Jagargunda-Jongaguda-Tarrem axis and the forces were deputed to intercept and neutralise them. The Maoists, however, drew the forces into a trap from three sides with heavy gunfire, they added. Even the rescue choppers could not land in the ambush area till around 2 pm on Saturday as heavy exchange of fire was taking place. The choppers could land only around 5 pm to pick up those who sustained injuries, the officials said.