A military spokesman said it accepted the authenticity of a video leaked on a dissident website that appeared to show soldiers torturing women soldiers, adding instructors had overstepped their authority for an undisclosed act of violating "military discipline".
"The investigation which is being carried out by the Sri Lanka Army Corps of Military Police has so far revealed that the video in question is an authentic one," military spokesman Brigadier Ruwan Wanigasooriya said in a statement.
"According to a preliminary report, the instructors (the troops) have punished the recruits for an act in violation of military discipline," Wanigasooriya added.
"However, the method adopted is not in accordance with standard procedures," he said.
The anti-establishment www.srilankaguardian.org website, which is blocked by internet providers in Sri Lanka but can be accessed through servers outside the country, published the 4.41-minute footage Friday, saying it had been filmed on a phone camera by another soldier.
The fuzzy footage showed women recruits being subjected to cruel and degrading treatment and sustained beatings by men in uniform.
The spokesman said the incident had taken place in October 2012 in the north-central district of Anuradhapura, further south of the war zone where fighting ended in May 2009 with the defeat of Tamil Tiger rebels.
"The individuals who carried out this excessive action had overstepped their mandate and acted in (sic) their own volition," he said.
It is the first time the military has accepted a leaked video showing torture as authentic, previously rejecting as fabrications several others allegedly showing executions of surrendered Tamil rebels and sexual abuse of female detainees.
The latest video came a week before the UN Human Rights Council was due to debate a US-led resolution pressing for an international investigation into allegations that Sri Lankan troops killed up to 40,000 civilians after ordering them into a no fire zone.
International rights groups have said Sri Lanka's government was complicit in many of the crimes.
A study published Friday by South African human rights lawyer and UN adviser, Yasmin Sooka, alleged that Sri Lankan troops carried out horrific sexual abuse of ethnic minority Tamils even after the end of the island's drawn out separatist war.
She said the "highest levels" of Sri Lanka's government were complicit in raping, torturing and abducting ethnic Tamils following the war and accused security forces of sexual abuse of Tamils, including forced oral sex and anal rape as well as water torture.
Colombo did not comment specifically on Sooka's report but has always denied such allegations and also insists that not a single civilian was killed by its troops while battling Tamil Tigers known for their trademark suicide bombings.
Colombo, in turn, has accused the defeated rebels of using civilians as human shields.