UN Security Council resolutions have called on Lebanon to disarm all militias on its soil, including Hizbullah guerrillas, and banned all unauthorized arms in Lebanon.
But Annan, in an eight-page status report to the UN Security Council, said there were "significant deficiencies" in equipment, training and coordination among four different Lebanese government services responsible for the borders.
"It is plain that there is a need for bilateral assistance to the government to enhance its border security capabilities," Annan wrote, asking nations to help Beirut.
The secretary general said that he continued to receive reports of illegal arms smuggling across the Lebanese-Syrian border but has been unable to verify them.
Still, his envoy, Terje Roed-Larsen, said earlier this month he had evidence of the smuggling but was unable to reveal his sources. Syria dismissed the charge as untrue.
Of the 13 incidents of unauthorized weaponry, two were reported earlier this month by UN Peacekeepers, who found 17 katyusha rockets and several explosive devices in the area of Rachaiya El-Foukhar and Berghouz as well as seven missiles, three rocket launchers and substantial amounts of ammunition, which the Lebanese army destroyed.
On another occasion, a UN demining team was challenged by two Hizbullah personnel in uniform, carrying AK-47 rifles. The Lebanese army arrested three of them, Annan's report said.
At the same time, Annan said Israeli aircraft entered Lebanese airspace, in violation of the ceasefire agreement, on almost a daily basis since his last report on Sept. 12.
UN peacekeepers recorded 14 illegal overflights on each of two days. In some cases, the violations "took the form of mock air attacks" on French peacekeeping bases, he said.
Israel insists the overflights are needed to guard against arms smuggling into Lebanon from neighboring Syria.
And Annan said that Israel had yet to provide the UN Interim Force in Lebanon, known as UNIFIL, with detailed data on cluster bombs. As of Nov. 20, some 822 cluster bomb strike sites have been discovered, an 80 percent increase since his Sept. 12 report, Annan said.
Annan reiterated that a "top priority" was the unconditional release of two Israeli soldiers captured in a cross-border raid on July 12 that prompted Israel's deadly military offensive into Lebanon.
His envoy for the prisoner swap, whom diplomats said was a German intelligence agent, was "engaged in an intensive effort with all parties to reach a resolution."
Annan also said he had sent a senior cartographer to review the material on the Shebaa Farms area, a strip of land occupied by Israel which Lebanon claims as its own but the United Nations says is part of Syria.
He said he took "careful note" but gave no recommendations on Lebanon's proposal to put the Shebaa Farms under UN jurisdiction until a permanent border was delineated.
Annan's report coincided with a massive street demonstration in Beirut by Hizbullah and its allies demanding a third of the seats in Prime Minister Fouad Siniora's cabinet, enough to veto decisions. Siniora and his supporters call the campaign a coup attempt led by neighboring Syria and Iran.