Israel carried out airstrikes deep into Lebanon during the night to Tuesday.
At least five people were killed, according to the London-based Syrian Human Rights Observatory (SOHR).
"Three Syrians working with Hezbollah and two Lebanese were killed in an Israeli attack on a convoy of tanker trucks that entered Lebanon at the Syrian border", SOHR chief Rami Abdel Rahman told AFP.
A further five people were injured and two are missing, he adds.
Israel's military says it attacked a military facility belonging to a logistics unit within the Islamist militia Hezbollah, near the city of Baalbek in eastern Lebanon during the night.
"The unit is used to smuggle weapons to and from Lebanon", the Israeli military announced, adding that the attack was in response to the downing of an Israeli drone over Lebanon on Monday.
Airstrikes have also been directed at targets in southern Lebanon, according to Israeli reports.
Israel and Iran-backed Lebanese Hezbollah have been exchanging fire almost daily since the Gaza War began following Hamas's terrorist attack on Israel in October.
The airstrike on the vehicle convoy is reported to have taken place near the city of Hermel and is thus the northernmost attack Israel has carried out in Lebanon since the Gaza War began, writes Haaretz.
Israeli aircraft have also regularly attacked targets in Syria linked to Hezbollah, which is allied with Hamas, during the war.
