Israel's ambassador to the UN Dan Gillerman sent a letter of concern to the UN following the discovery of a cluster of explosive devices along the border between Israel and Lebanon, reminding them of their responsibility to maintain security in the region. "We regard this with great concern, and feel, on the whole, that the situation on the northern border is very vulnerable," Gillerman told The Jerusalem Post Tuesday. "The UN and the international community made a commitment, and should make every effort to implement Resolution 1701." The bombs found on Monday, just north of Avivim, along the Blue Line (the international border between Israel and Lebanon), were said to have been planted there by Hizbullah just a few days ago. The bombs weighed around 15 to 20 kilograms each and were disguised as boulders to blend in with the surrounding terrain. Gillerman's letter, sent Monday, said the recent findings were "gravely reminiscent of the events of 12 July 2006, when Hizbullah terrorists violated Israeli sovereignty and crossed the Blue Line into Israel and kidnapped two Israeli soldiers." The consequences, he said, "could considerably undermine regional stability." According to UN Spokesman Farhan Haq, UNIFIL carried out an investigation on Tuesday, and found that a few improvised explosive devices were located on the Lebanese side in the immediate vicinity of the Blue Line. "UNIFIL is not in a position to determine whether these devices were laid before or after the cessation of hostilities on the 14 of August 2006," said Haq. Gillerman stressed that it was the UN's responsibility to make sure that forces on the ground "are much more vigilant," and that they "tighten up control." Otherwise, he said "the whole region could flare up again." "I think they (UN) are very careful but they are taking it seriously," Gillerman said. "We are constantly having talks, making sure they treat this very seriously."