The IDF has started using undercover elite border policemen to quell anti-fence demonstrations in the West Bank, sources in the Central Command said on Tuesday. Last Friday, officers from the Border Police's elite YAMAS undercover unit disguised themselves as Palestinians and stood among a crowd of demonstrators from Nil'in who were protesting against the construction of the security fence nearby. In a video posted on the Web site of the International Solidarity Movement (ISM), three Palestinians wearing shirts over their heads to cover their faces are seen using a metal cutter to dismantle part of the chain-linked security barrier. Suddenly, two other demonstrators approach, pull out guns and knock two of the Palestinian demonstrators to the ground. The crowd realizes that the so-called demonstrators are actually undercover policemen and begins hurling rocks at them. The policemen are then seen firing several shots into the air before herding away the two captured demonstrators. Sources in the Central Command confirmed on Tuesday that undercover YAMAS border policemen were used to help suppress the demonstrators at Nil'in as part of the IDF's increasing efforts to prevent clashes between Palestinian demonstrators and security forces. On Friday, the IDF also used its "skunk bomb" - a foul-smelling liquid that is sprayed on protesters, causing them to flee due to the intense odor.