The UN closed its office in Sri Lanka and recalled its head to New York for consultations as government-sanctioned protests against an investigation into alleged war crimes went into their third day, a UN office spokesman said on Friday.
UN Secretary General,Mr Ban Ki-moon, on Thursday said it was "unacceptable" that Sri Lankan authorities have failed to prevent the disruption of UN activities in the country.
Mr Ban ordered Neil Buhne, the UN special envoy for Sri Lanka, to return to UN headquarters in New York for consultations and to close the UN Development Programme (UNDP) office in Colombo.
Construction minister, Ms Wimal Weerawansa and members of his National Freedom Front (NFF) party, a member of the governing coalition, launched a protest outside the UN office in Colombo on Tuesday.
Ms Weerawansa has begun a hunger strike Thursday morning and vowed continue his campaign until Ban reverses his decision to name a panel to investigate alleged war crimes against Tamil civilians.
Ban appointed a three-member expert panel last month, mandated to advise him on measures to deal with the Sri Lankan government's accountability for its actions during the final stage in the 26-year civil war to defeat Tamil rebels last year. Thousands of civilians were reportedly killed.
The UN office in Colombo houses the UNDP which is the main agency funding UN projects on the island.
The US Department of State reiterated its support for the panel, saying it was an opportunity for Sri Lanka to hold an accountable process and take advantage of the expert group.
"We feel like it's in Sri Lanka's best interest to accept these people and their expert advice and that's offered in good faith," State Department spokesman, Mr Mark Toner said.
While resolving the current impasse was a matter between the UN and Sri Lanka and he could not speak for the UN, Toner said Washington supported the involvement of the UN group.