The Tamil National Alliance (TNA) said the resolution gives specific time frame to Sri Lanka and the Office of the High Commissioner for Human Rights to report on the successful implementation of the 2015 resolution.
At the same time, the TNA warned that, "the Tamil people have reached their limits of tolerance, and urge that their deprivation and suffering on these several issues be brought to an early end".
Thirty-six more countries co-sponsored the UNHRC resolution which was adopted without a vote in Geneva yesterday. This was in addition to the original sponsors - the US, the UK, Montenegro and Macedonia. They recognised Sri Lanka had made good progress in its reconciliation attempts.
The TNA's move supporting more time for Sri Lanka was criticised by the Tamil hardline diaspora groups which said that they have lost confidence in the Sri Lankan government.
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Sri Lanka was granted 18 months by a UNHRC resolution in October 2015 to initiate a credible investigation into the over three-decades long civil war with the LTTE.
The two-year time was allowed despite strong opposition from the Tamil lobby who cited inaction by the government to show genuine commitment to the resolution.
UN rights council had called for international judges to help investigate possible war crimes to guarantee impartiality.
According to the UN figures, up to 40,000 civilians were killed by the security forces during former president Mahinda Rajapaksa's regime that brought an end to the conflict with the defeat of LTTE in 2009.