The jawans of the COBRA unit were ambushed in the IED blast after which an encounter started between the two resulting in the killing of three naxals, they said.
The incident was reported from Chakarbanda forests of the said district, bordering Imamganj.
Some arms and ammunition were also recovered from the site.
Officials said the casualties may rise as some of the jawans of the Commando Battalion for Resolute Action (COBRA) were critically injured in a fierce gun battle, which was still raging.
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The jawans belonged to the 205th COBRA battalion and were deployed in the state for conducting anti-naxal operations.
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CRPF Director General K Durga Prasad and other senior
officers are expected to visit the ambush site today.
Officials said over a dozen IED blasts were triggered by the Naxals.
The martyred CRPF men have been identified as Head Constables Anil Kumar Singh, a resident of Buxar in Bihar and K Opendra Singh of Thoubal, Manipur, Constables Sinod Kumar of Azamgarh in Uttar Pradesh, Ramesh Kumar from Hoshiarpur in Punjab, Diwakar Kumar from Khagariya in Bihar, Polash Mondal from South Denajpur in West Bengal, Deepak Ghosh of Nadia in West Bengal, Manoj Kumar of Betul in Madhya Pradesh, Harvender Panwar of Muzaffarnagar in UP and Ravi Kumar from Siwan in Bihar.