COLOMBO: Sri Lanka was under new pressure today to submit to a war crimes investigation after the United Nations authenticated a video allegedly showing prisoners being executed by troops last year. The government in Colombo has faced repeated calls for a probe from Western countries and rights groups ever since it launched a final offensive to crush Tamil Tiger separatist rebels in the country’s northeast in early 2009. The assault brought an end to a 37-year-old ethnic conflict that had claimed 100,000 lives since 1972, but hurt the reputation of the country abroad amid criticism of the conduct and tactics of government forces. The UN estimates that 7,000 civilians perished during the first four months of last year, though this figure is disputed by the government. On Thursday, UN human rights envoy Philip Alston concluded that video footage said to be of Sri Lankan troops executing unarmed Tamil Tiger rebels last year was authentic and urged Colombo to accept a war crimes probe. Reacting today, Sri Lankan Human Rights Minister Mahinda Samarasinghe again dismissed the video as a fraud and accused Alston of leading a personal crusade against the country. “Philip Alston is on a crusade of his own to force an international (war crimes) inquiry against Sri Lanka,” Samarasinghe told AFP. “We object to the procedure he followed. He should have shared his information with us first.” He added: “As far as we are concerned, the video is not genuine and it has been doctored.” Sri Lanka has always resisted calls to probe its rights record, arguing that there are no grounds for an investigation given that there were no civilian casualties or extrajudicial killings. In May last year, Colombo managed to stave off a resolution condemning it at the UN Human Rights Council thanks to the backing of China. But new charges emerged last month when the former army chief, Sarath Fonseka, alleged that troops had been ordered by a top defence official to execute surrendering rebels, a charge the government vehemently denies. The government accused Fonseka, who is challenging President Mahinda Rajapakse in the January 26 national election, of “betraying” the country and making the statement for political gain. Three Tiger political wing leaders who were arranging their surrender with UN assistance were shot dead on May 17, according to official reports. The government maintained that they were killed by the guerrillas themselves. Secretary General Ban Ki-moon said, through his spokesman Martin Nesirky in New York, that “a full and impartial investigation into allegations of human rights is critical if we are to confront impunity” and bring justice.