New Delhi: In one of the biggest attacks by Naxals on security forces in the last few years, 10 commandos of the elite CoBRA battalion of the CRPF were killed by a group of 200 heavily-armed Maoists in the forests of Aurangabad district in Bihar in a fierce encounter that lasted several hours on Monday.

Five commandos were injured while three Naxals were killed in the operation which led to recovery of sophisticated weapons like under barrel grenade launchers, as also AK and INSAS assault rifles from the Maoists.

Both Prime Minister Narendra Modi and Home Minister Rajnath Singh expressed grief over the incident. The Home Minister also spoke to Bihar Chief Minister Nitish Kumar in wake of the incident and assured him of all possible assistance from the Centre.

Mr Singh also directed CRPF DG K. Durga Prasad and senior officers to rush to Aurangabad. Additional security forces have already been rushed to the area for search and combing operations.

“This is one of the biggest attacks on the CoBRA unit, a specialised force raised in 2008 for undertaking guerrilla operations against Naxals in forest areas. What is surprising is that the incident happened in Bihar this time as most of the big Naxal attacks have taken place in Chhattisgarh or Jharkhand. This is a worrying trend and needs to be investigated thoroughly,’’ a senior home ministry official said.

Security experts agreed that the recent incident is an indication of the ease with which Naxals are moving across States borders and this may force the security forces to review their strategy of hot pursuit.