An Indian Reserve Battalion (IRB) officer was on Saturday critically injured in a clash with Gorkha Janmukti Morcha (GJM) supporters in the northern West Bengal hills.Kiran Tamang, Assistant Commander of IRB, was later brought to Siliguri for treatment, Mrinal Ghosh, Commandant IRB Second battalion, said.West Bengal Chief Minister Mamata Banerjee, commenting on the incident, said in Kolkata: "As per the reports we got, Kiran Tamang is critically injured. He is not dead."Earlier she had said the Assistant Commander was dead.Meanwhile, the GJM claimed two of its supporters were killed and five critically injured in police firing."As of now two persons were killed and five are critically injured. We are searching for our men and women," GJM assistant general secretary Binay Tamang said.Police have denied firing at the protesters."Police did not fire. GJM set fire to our vehicles. We are looking into the incident," ADG law and order Anuj Sharma.The GJM sponsored indefinite shutdown in the northern Bengal hills, which entered the sixth day on Saturday, saw fresh violence and protests after GJM's Tamang alleged his house had been raided and vandalised by police.