Israel's continued flights over Lebanon's airspace are in violation of the recent UN resolution and compromise efforts to stabilize the situation along the border between the two countries where UN peacekeepers have come across 13 instances of unauthorized arms or material since September, Secretary-General Kofi Annan said. Despite these incidents, Annan said in a letter to the UN Security Council on Friday that the August cease-fire that ended this summer's Israeli-Hizbullah war has been maintained "and there were no serious incidents or confrontations." But he said UN peacekeepers reported air violations by Israeli jets and unmanned aerial vehicles "almost on a daily basis," which Lebanon has protested as a serious violation of its sovereignty. Israel maintains the overflights are a security measure, and Defense Minister Amir Peretz has linked the flights to the return of two Israeli soldiers captured by Hizbullah on July 12, Annan said. While "mindful" of Israel's motivations, he said, the overflights violate UN resolutions and "undermine the credibility" of both the UN force and the Lebanese army. They also "compromise overall efforts to stabilize the situation in the south and efforts to build trust and confidence generally," he said. The secretary-general said he continued to make the unconditional release of the captured Israeli soldiers and the issue of Lebanese soldiers detained in Israel a top priority. No shooting incidents have been reported across the international border since UNIFIL began beefing up with the arrival of French forces Aug. 19, shortly after a UN cease-fire ended the Israeli-Hizbullah war. But Annan said UNIFIL recorded a number of minor ground violations of the UN-drawn boundary known as the Blue Line by Israelis and Lebanese. Regarding the disputed Shaba Farms area on the Lebanon-Syria-Israel border, Annan said he has appointed a senior cartographer to take the lead in developing "an accurate territorial definition" of what the area encompasses. In his letter to the Security Council president, Annan said, UNIFIL and the Lebanese army "have seen sporadic evidence of the presence of unauthorized armed personnel, assets and/or weapons." On one occasion, he said, a UNIFIL sapper team was challenged by two Hizbullah members in combat uniforms carrying AK47 rifles. UNIFIL notified the Lebanese army who arrested three suspects the following day, he said. "Since early September, there have been 13 instances where UNIFIL came across unauthorized arms or related material in its area of operation," Annan said. The two most noteworthy incidents, he said, were the discovery of 17 katyusha rockets and several improvised explosive devices in Rachaiya El-Foukhar, and the discovery of a weapons cache containing seven missiles, three rocket launchers and a substantial amount of ammunition in the area of Bourhoz. On every occasion, Annan said, UNIFIL informed the Lebanese army which either confiscated or destroyed the material. While the Lebanese authorities reported that they have undertaken a variety of measures to secure their borders and entry points, Annan said, "the United Nations continues to receive reports of illegal arms smuggling across the Lebanese-Syrian border." The UN has not been able to verify the reports, he said. Annan noted, however, that UN border police experts had found "significant deficiencies" in Lebanon's equipment and training of its border officials. "There is a need for bilateral assistance to the government to enhance its border security capabilities," he said. Annan reiterated his call for Israel to provide "detailed firing date on its use of cluster munitions."