UNITED NATIONS - UN chief Ban Ki-moon rejected on Wednesday remarks by a UN rights investigator, who suggested the Boston bombings were a response to US foreign policy, and warned UN envoys that their public comments could undermine the world body's credibility.Richard Falk, UN special rapporteur for human rights in the occupied Palestinian territories, wrote on his blog on Sunday that "the American global domination project is bound to generate all kinds of resistance in the post-colonial world."US officials say ethnic Chechen brothers, Tamerlan and Dzhokhar Tsarnaev, planted and detonated two pressure-cooker bombs near the finish line of the Boston Marathon on April 15, killing three people and injuring 264. Ten people lost limbs."In some respects, the United States has been fortunate not to experience worse blowbacks, and these may yet happen, especially if there is no disposition to rethink US relations to others in the world," Falk, a US academic, wrote.NBC has reported, citing federal law enforcement officials, that the Tsarnaev brothers had been motivated by the US wars in Afghanistan and Iraq.Ban's spokesman, Martin Nesirky, told reporters that the secretary-general rejected Falk's comments and pointed out that Ban did not appoint Falk. He was appointed by the Geneva-based Human Rights Council to his position in 2008."The secretary-general is hopeful that special rapporteurs such as Mr Falk, understand that while they have independent status, their public comments can undermine the credibility and the work of the United Nations," Nesirky said.Falk has long been a controversial figure. In 2011, he wrote on his blog that there had been an "apparent cover-up" by US authorities over the Sept. 11, 2001 attacks. He also posted an anti-Semitic cartoon, which was later removed.The United States mission to the United Nations on Tuesday rejected Falk's comments on the Boston marathon bombings as "provocative and offensive.""The United States has previously called for Mr. Falk's resignation for his numerous outrageous statements, and these comments underscore once more the absurdity of his service as a UN special rapporteur," Erin Pelton, spokeswoman for US mission to the United Nations, said in a statement.