BEIRUT – Israel launched a rare airstrike inside Syria, U.S. officials said Wednesday, targeting a convoy believed to contain anti-aircraft weapons bound for Hezbollah militants in Lebanon. The attack adds a potentially flammable new element to tensions already heightened by Syria's civil war.

It was the latest salvo in Israel's long-running effort to disrupt the Shiite militia's quest to build an arsenal capable of defending against Israel's air force and spreading destruction inside the Jewish state.

Regional security officials said the strike, which occurred overnight Tuesday, targeted a site near the Lebanese border, while a Syrian army statement said it destroyed a military research center northwest of the capital, Damascus. They appeared to be referring to the same incident.