Israeli strikes late on Tuesday targeted Lebanon's three northern border crossings with Syria for the first time, Lebanon's caretaker transport minister Ali Hamieh told Reuters.
The strikes came hours before a ceasefire took effect to halt hostilities between Lebanese armed group Hezbollah and Israel.
Hamieh said it was not immediately clear whether the roads had been cut off as a result of the strikes. Israeli raids on Lebanon's eastern crossings in recent weeks had already sealed off those routes into Syria.
Syria's state news agency reported four civilians and two soldiers were killed, and 12 people were wounded including children, women and workers in the Syrian Red Crescent.
The Red Crescent said earlier a volunteer was killed and another was injured in "the aggression that targeted Al-Dabousyeh and Al-Arida crossings ... as they were performing their humanitarian duty of rescuing the wounded early on Wednesday."
The strike damaged several ambulances and work points, it added in a statement.
Syrian state TV reported the Israeli strike hit the Arida and Dabousieh border crossings with Lebanon.
The Israeli military did not immediately comment. It has previously stated that it targets what it says are Iran-linked sites in Syria as part of a broader campaign to curb the influence of Iran and its ally Hezbollah in the region.
Separately, US Central Command (CENTCOM) said on Tuesday that it struck an Iranian-aligned militia weapons storage facility in Syria in response to an Iranian-aligned attack against US forces in the country on Monday.
