The Lebanese militia Hezbollah fired a volley of rockets toward a small military base in northern Israel on Saturday morning, in what the group said was an initial response to the assassination of a senior Hamas commander in Lebanon five days ago that has raised fears of a wider conflagration.

Hezbollah said in a statement that the strikes had caused casualties, but there were no immediate Israeli reports of injuries and the assault was initially perceived by analysts as more of a symbolic response to the assassination than a significant escalation.

The Israeli military said in a statement that roughly 40 rockets had been fired from Lebanon toward Mount Meron, an area housing a military radar station that is roughly five miles south of the Israel-Lebanon border. The military said that it had responded by striking a militant group in Lebanon that had been involved in the rocket fire.

Hezbollah could still respond with a more forceful attack, while Hamas has not retaliated for the assassination of the senior commander, Saleh al-Arouri. Mr. al-Arouri was killed on Tuesday in Beirut in an attack attributed by Hamas and Hezbollah to Israel. Lebanese and U.S. officials have also ascribed the attack to Israel, though Israel has not confirmed that.

At least for now, the limited nature of the exchange on Saturday tempered fears that Mr. al-Arouri’s killing would immediately lead to a major escalation between Hezbollah and Israel.

The exchange came as Antony J. Blinken, the U.S. secretary of state, and Josep Borrell Fontelles, the European Union’s top diplomat, separately visited the region in an effort to reduce the risk of a regional war breaking out.

Hamas attacked Israel from Gaza on Oct. 7, leading Israel to respond in Gaza with one of the deadliest military campaigns this century. At the same time, Israel has been engaged in a low-level second conflict with Hezbollah, an ally of Hamas and a fellow proxy of Iran.

That second front has mostly been contained within the border areas of northern Israel and southern Lebanon, with both sides generally limiting their strikes to within a few miles of the border, far from major cities like Tel Aviv or Beirut.

But the killing of Mr. al-Arouri, in a building deep inside a Hezbollah stronghold in southern Beirut, prompted fears that Hezbollah might respond with a more forceful attack of its own on major cities in central Israel.

Mr. Blinken was in Turkey on Saturday morning, while Mr. Borrell was visiting Lebanon, where he said his priority was to “avoid regional escalation and to advance diplomatic efforts” for peace in the region.

Euan Ward contributed reporting from Beirut, Lebanon.