The Left-wing extremists used the technique to blow-up a civilian bus on Monday in which at least 50 people were feared killed, officials said. The Maoists staged the attack by digging a tunnel on either side of the road, to reach the concrete top from below to plant the IED, they said.
The IED is understood to have been planted days before Monday's attack and was triggered by the Naxals who were armed with real-time intelligence that Special Police Officers were traveling in the civilian bus.
"In this way, they do not disturb the crust, so as to avoid any suspicion. The signs of dredging on the sides of the road can be easily wiped off. In this way, they can quickly fit an IED and carry out the blast in the most effective way," officials said.
In a similar use of IEDs last week, the Maoists had blown up an armoured vehicle, in which eight Central Reserve Police Force personnel were killed. Top police officials said the same technique was used by the LTTE against the Sri Lankan forces.
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