The comments by Dalas Alahapperuma, minister of youth affairs, came a day after the U.N. Human Rights Commission approved the U.S.-backed resolution. The resolution followed a U.N. report alleging Sri Lanka's government may be to blame for tens of thousands of civilian deaths during the military campaign to defeat the separatist Tamil Tiger rebels.
Alahapperuma told reporters that the UNHRC was being misused by "imperialists" to divide Sri Lanka. He did not elaborate, but such comments usually refer to the creation of a separate state for minority ethnic Tamils.
Rights groups and foreign governments have called for an international probe of the civil war, which ended in 2009 after government troops crushed the rebels. The rebels fought for a separate state for the Tamils for more than a quarter-century.
By a 25-13 vote, and with eight abstentions, the 47-nation UNHRC urged the South Asian nation "to initiate credible and independent actions" to ensure justice and accountability in the aftermath of the war. Those in favor included India and Brazil, while those opposed included Pakistan, Venezuela and Indonesia.
A similar resolution in March 2012 called on Sri Lanka to probe allegations of summary executions, kidnappings and other abuses, but stopped short of calling for an international investigation.
Sri Lanka and its allies opposed both resolutions, saying they unduly interfered in the country's domestic affairs and could hinder its reconciliation process.
The Sri Lankan government has argued that its own investigation should suffice. A Sri Lankan commission report, released in December 2011, cleared government forces of wrongdoing.
Rights groups and government critics say Sri Lankan President Mahinda Rajapaksa's administration has ignored previous calls for accountability—including last year's resolution—and that it has dragged its feet in implementing even the limited recommendations made by its own war panel.
Thursday's resolution was watered down before it passed to add language praising Sri Lanka and to remove other passages, such as those calling on the government to give unfettered access to U.N. special investigators and others. Backers of the resolution argued that credible probes into alleged crimes are an important step to heal the nation.