Israeli medics say at least 10 people were killed in a barrage of rockets fired from Lebanon into the Israeli-occupied Golan Heights.
Eli Bin, head of the Magen David Adom emergency service, said the victims were between the ages of 10 and 20.
The Israeli military said around 40 rockets were fired by the Lebanese group Hezbollahand one hit the football pitch in Majdal Shams, but the group denied it.
"There is no doubt that Hezbollah crossed all red lines," Israeli Foreign Minister Israel Katz told Channel 12 news. "We are facing an all-out war."
The strike on Majdal Shams followed an earlier Israeli airstrike on Kfarkila in southern Lebanon in which four suspected militants were killed.
The Israeli military said its aircraft had targeted a military structure belonging to Hezbollah. Missile strike on Golan Heights raises fears of escalation.