The Israel Defense Forces on Sunday said the military struck Hezbollah targets "deep inside" Lebanon overnight.

The Israeli Air Force targeted "weapons caches and terrorist infrastructure" in about a half-dozen areas in southern Lebanon, the military said in a statement.

The Israeli attack on Hezbollah infrastructure followed a deadly strike within Israel on Saturday. Hezbollah denied responsibility for the attack in Majdal Shams, a town in the Israeli-occupied Golan Heights.

But an Israeli official said the rocket that struck a sports field, killing 12 people and injuring more than a dozen others, had been fired by Hezbollah.

"We know to say that it is a Falaq rocket with a 53 kg warhead. This is a Hezbollah rocket," Lt. Gen. Herzi Halevi, IDF chief of the general staff, said in a statement. "And whoever launches such a rocket into a built-up area wants to kill civilians, wants to kill children."

Israeli Prime Minister Benjamin Netanyahu released a video statement following the attack on occupied Golan Heights which the IDF says has killed 12 people, all teenagers and young adults.

The prime minister said he will return to Israel early and convene the Security Cabinet as soon as he arrives.

"The State of Israel will not let this pass in silence. We will not overlook this," he said in Hebrew.

-ABC News' Victoria Beaulé

Israel is preparing a "response" against Hezbollah after a number of strikes on the Israeli-occupied Golan Heights killed at least 10 people, Israel Defense Forces spokesperson Daniel Hagari said in a statement Saturday. Hezbollah has denied responsibility for the attack.

Israel has continued to accuse Hezbollah of firing the strikes despite its denial.

"This is an attack that comes after attack in the north for more than 9 months, Hezbollah is attacking our citizens in the north firing thousands of rockets and missiles and UAVs at northern Israel. Targeting families, homes, and communities. The IDF is currently holding a situational assessment and we will prepare for a response against Hezbollah. We will finish our assessments and we will act," Hagari said in a video statement.

-ABC News' Bruno Nota

A senior Israeli official traveling with Prime Minister Benjamin Netanyahu issued a warning to Hezbollah hours after an attack on the occupied Golan Heights killed at least 10 people.

"Hezbollah will pay a heavy price. Hezbollah, like Hamas and the other Iranian proxies target civilians and do it premeditatedly," the senior official told ABC News.

-ABC News' Eric Avram