The Lebanese army fired anti-aircraft artillery at Israeli warplanes as they flew over Beirut yesterday, in Israel’s most flagrant violation of the U.N. resolution that brought an end to this summer’s 34-day war with Hezbollah.

Eight Israeli air force jets crossed into Lebanese airspace early Tuesday, swooping to low altitudes over the capital’s Shiite-dominated southern suburbs that were devastated by the conflict. Although the jets did not open fire, they flew over the area’s crater-lined streets six times in half an hour, bringing stunned residents on to rooftops to watch.

Israeli jets were also reported to have made sonic booms over Lebanon’s southern port city of Tyre. Geir Pederson, the U.N. secretary-general’s personal representative for Lebanon, said the flights were a clear violation of U.N. Resolution 1701, which ended this summer’s war.

Israel insists that it will continue to fly over Lebanon in an effort to prevent weapons being smuggled into southern Lebanon from Syria, which is a contravention of the same resolution.

“The secretary general takes these violations extremely seriously, and they are a great concern for us all,” Mr. Pederson said in Beirut yesterday. “We are discussing these violations with Israel and taking diplomatic measures to see that they do not continue.”

Javier Solana, the European Union’s foreign policy chief, said Israel’s operations risked derailing the U.N.-brokered ceasefire in Lebanon.

“I spoke with Israeli authorities saying they should stop operations that, in our judgment, and based on the resolution, put a solution at risk,” said Mr. Solana.

Evidence of a violation of an arms embargo in southern Lebanon came when Terje Roed-Larsen, the U.N. Middle East envoy, showed that sources within the Lebanese government had informed him of arms smuggling across the border from Syria.

While Mr. Roed-Larsen admitted that he was unable to independently verify the report, it is widely believed that Syria and Iran are helping Hezbollah rebuild its arsenal following the war.

The information about the smuggling was provided by non-Hezbollah members of the Beirut government who are trying, so far unsuccessfully, to take control of the mainly Shiite South, where their authority has not held for decades. The sources refused to be identified for fear of assassination.

John Bolton, America’s ambassador to the United Nations, who accused Syria and Iran of trying to undermine the Beirut government, made Mr. Roed-Larsen’s comments public.