BEIRUT, Lebanon — Amid the chaos of Syria's civil war, Hezbollah has been moving long-range missiles to Lebanon from bases where it had stored them inside Syria, including long-range Scud D missiles that can strike deep into Israel, according to an Israeli national security analyst.

The analyst, Ronen Bergman, who has close contacts with Israeli intelligence officials, said that despite Israel's undeclared campaign of airstrikes in Syria to stop new deliveries, most of the long-range, surface-to-surface missiles given to Hezbollah by its allies Iran and Syria have been disassembled and moved to Lebanon.

Hezbollah, the Shiite militia that is also Lebanon's strongest political party, has a network of bases that were built inside Syria, near the border with Lebanon, to give the group strategic depth and to store the missiles, Mr. Bergman said. But with a nearly three-year insurgency threatening President Bashar al-Assad of Syria, an ally of the militia's, keeping the missiles in Syria is no longer as secure, Mr. Bergman said.

The missiles being moved, he said, include Scud Ds, shorter-range Scud Cs, medium-range Fateh rockets that were made in Iran, Fajr rockets and antiaircraft weapons that are fired from the shoulder.

Israel is concerned that Hezbollah not acquire what it considers game-changing strategic weapons during the Syria chaos.

Mr. Bergman said that on the first day of the war between Hezbollah and Israel in 2006, the chief of the intelligence agency Mossad at the time, Meir Dagan, advised the government not to start an attack on Hezbollah in Lebanon without first hitting the militia's bases in Syria, which were built on the strategy that Israel would not dare to strike Syria.

Mr. Bergman's account corroborated one given by a Syrian military officer in December 2012, at a time when rebels seemed to have momentum in their advances on Damascus.

The officer, who spoke over Skype from Damascus, said he no longer supported the government and wanted to defect but was waiting for the right moment, in the meantime acting as an informant for the rebels. He said government forces were dismantling strategic weapons and sending them to two locations "for safekeeping": the coastal province of Tartous that the government holds and south Lebanon, where Hezbollah holds sway.

The weapons, he said, were being sent in tractor-trailers with special coolers. The officer said his information came from another officer who was loyal to the regime and with whom he had close relations, and from his own limited observations of the trucks being used to move the weapons.

After several contacts, the officer could no longer be reached, and the information could not be verified.