"Never at anytime during Sri Lanka Army's 25 years of counter terrorism operations has it resorted to the use of illegal weapons," military spokesman Brigadier Ruwan Wanigasooriya said.
He was responding to accusations levelled by Tamil groups that the army had used chemical weapons and cluster bombs during the battle.
Rayappu Jospeh, a bishop from northeastern Mannar had reportedly told visiting US Ambassador-at-large on Criminal Justice Stephen J Rapp that the army had used the chemical weapons.
Sri Lanka is expected to encounter another resolution at the UNHRC in late March - the third such resolution in as many years to be moved by the US and backed by India.
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Similarly, Wanigasooriya dismissed allegations that the military had increased patrolling in northern Jaffna peninsula.
"This is incorrect as we have only streamlined military activity in the north to ensure ease of civilian life. This meant that we reduced a number of military check points," Wanigasooriya said.