COLOMBO - The UN's top rights official begins a fact-finding mission to Sri Lanka on Sunday after the government dropped public hostility towards her and promised access to former war zones.
Navi Pillay, who has previously been accused by Colombo of overstepping her mandate, is on a week-long mission that will include talks with President Mahinda Rajapakse and trips to the former war zones in the north and east.
The government's U-turn came as Canada leads calls for a boycott of a Commonwealth summit scheduled to take place in the Sri Lankan capital later this year.
Sri Lanka has resisted pressure from the UN and Western nations for a credible investigation into allegations that up to 40,000 civilians were killed in the final months of its separatist war, which ended in 2009.
A no-holds-barred military offensive crushed Tamil Tiger rebels who at the height of their power controlled a third of Sri Lanka's territory. Rajapakse has since been dogged by claims of indiscriminate killing of ethnic Tamils.
Tamil groups are banking on Pillay's first visit to Sri Lanka to revive calls for a war crimes probe.
"We will take up with her the question of accountability, the issue of thousands of missing people, the militarisation of Tamil areas and the lack of political freedoms," Tamil National Alliance lawmaker Suresh Premachandran told AFP.
Pillay's visit follows two resolutions by the UN Human Rights Council (UNHRC) in as many years demanding Colombo hold an independent investigation into "credible allegations" that troops shelled hospitals and refugee camps, and executed surrendering rebels.
The government insists that its troops did not kill civilians and has slammed the UNHRC for its "ill-timed and unwarranted" resolutions.
Pro-government activists have also led demonstrations outside the UN offices in Colombo, accusing Pillay of being a US stooge.
But the government's change of heart in welcoming the rights chief could signal a desire to improve its image ahead of a crucial UNHRC session in September and the Commonwealth Heads of Government Meeting in November.
"She has not accepted what we have done (to improve the rights situation)," Sri Lanka's human rights envoy to the UN, Mahinda Samarasinghe, told reporters in Colombo last week.
"So we are showing her what we have done and we are also allowing her to visit anywhere and meet anyone."