The Lebanese government has asked the United States to urge restraint from Israel, Lebanon's foreign minister Abdallah Bou Habib told Reuters on Sunday, as tensions build following an attack blamed on Hezbollah that killed 12 children and teenagers in the Israeli-occupied Golan Heights.

Bou Habib said the US had asked the Lebanese government to pass on a message to Hezbollah to show restraint as well. 

Israel said on Sunday it would strike hard against Hezbollah after accusing it of waging the attack. 

Hezbollah had earlier announced it had fired rockets at Israeli military sites, but swiftly denied involvement in the attack on Majdal Shams, saying it had "absolutely nothing to do with the incident, and categorically denies all false allegations in this regard."

"Contrary to its denials, Hezbollah is the entity that is unequivocally responsible for yesterday's massacre," Israel's foreign ministry said. "The rocket that murdered our boys and girls was an Iranian rocket and Hezbollah is the only terror organization which has those in its arsenal."

An Israeli military spokesperson had earlier told reporters that forensics showed the rocket was an Iranian-made Falaq-1. Hezbollah had announced firing a Falaq-1 missile on Saturday, saying it had aimed at an Israeli military headquarters.

Defence Minister Yoav Gallant visited Majdal Shams and said: "We will hit the enemy hard."

The Israeli military said the rocket launch was carried out from an area located north of the village of Chebaa in southern Lebanon.

Hezbollah was on high alert on Sunday, two security sources told Reuters, adding that the group has preemptively cleared out some key sites in both Lebanon's south and the eastern Bekaa Valley in the event of a possible attack by Israel.