Israel launched a deadly strike in a densely populated Beirut suburb on Tuesday in retaliation for a rocket attack in the Israeli-controlled Golan Heights that it blamed Hezbollah for and that killed 12 children and teenagers on a soccer field.

The target of the Israeli strike in a southern suburb of Lebanon’s capital was Fuad Shukr, a senior official who serves as a close adviser to Hezbollah’s leader, Hassan Nasrallah, according to three Israeli security officials who spoke on the condition of anonymity to discuss sensitive details.

The Israel Defense Forces later said in a statement that its fighter jets had “eliminated” Mr. Shukr, but there was no confirmation from Hezbollah, the powerful Iran-backed group, and the claim could not be independently verified.

Hezbollah has denied carrying out the attack in the Golan Heights on Saturday. The latest strikes were likely to fuel concerns that Israel’s long-running conflict with the group could escalate into a full-blown war even as Israel wages a military offensive against Hamas in the Gaza Strip after that group led a deadly assault in Israel on Oct. 7.

The attack on Tuesday is believed to be the first time since the war with Hamas began that Israel has targeted Hezbollah in Beirut. In January, an Israeli airstrike in a Beirut suburb killed Saleh al-Arouri, a senior leader of Hamas, which is also backed by Iran.

The strike on Tuesday killed at least three other people — a woman and two children — and wounded at least 74 others, five critically, according to Lebanon’s Ministry of Health. Officials were still searching the rubble for other victims, the ministry said.