The accused Rammohan Reddy, Narsimha Reddy and M Chandra will also have to pay a fine of Rs 500 each, prosecutor Sudhakar Babu said.
On October 1, 2003, Maoists triggered off a claymore mine blast near Alipiri when Naidu's convoy was heading for Tirumala. Naidu suffered injuries in the blast.
"The trio who were on bail were taken into custody after the judgement. They pleaded for reduction of sentence saying they were surrendered Naxals," Sudhakar Babu said.