Israel "delivered crushing blows to all our enemies", Prime Minister Benjamin Netanyahu said, explicitly mentioning the killing of Hezbollah leader Fouad Shukur in south Beirut.

Netanyahu's televised statement on Wednesday lasted for approximately five minutes and did not make any reference to the killing of Hamas chief Ismail Haniyeh in Tehran.

An Israeli strike that killed a Hezbollah commander in Beirut and the killing of the political leader of Hamas in Tehran "don't help" regional tensions but there are no signs of an imminent wider conflict, the White House said.

"These reports over the last 24, 48 hours certainly don't help with the temperature going down," National Security Council spokesman John Kirby told reporters Wednesday when asked about the attacks.

Hundreds of mourners on Wednesday chanted "death to Israel" and "America is the Great Satan" at the funeral of two children killed in an Israeli strike on Hezbollah's stronghold in southern Beirut the day before.

The Israeli military said the strike had "eliminated" Fouad Shukur, a top Hezbollah commander it blamed for carrying out a weekend rocket attack on the Israeli-annexed Golan Heights that killed 12 children.

Air France and low-cost carrier Transavia France said Wednesday their flights between Paris and Beirut would remain suspended till the weekend due to the "security situation" in Lebanon.

The two airlines had planned to resume flights on Wednesday, but said they will now remain grounded until Saturday.

Switzerland has urged its nationals to leave Lebanon, noting the highly volatile situation in the country.

Hezbollah confirmed Wednesday that Israel killed a top commander after a rare strike in Beirut.

U.N. Secretary-General Antonio Guterres has denounced strikes on Beirut and Tehran as a "dangerous escalation," after Israel targeted a top Hezbollah commander in Lebanon and Hamas said its political chief was killed in Iran.

"The scretary-general believes that the attacks we have seen in South Beirut and Tehran represent a dangerous escalation at a moment in which all efforts should instead be leading to a ceasefire in Gaza" and "the release of all Israeli hostages," spokesman Stephane Dujarric said in a statement.

The United States has raised its travel advisory on Lebanon to its highest "do not travel" classification, citing rising tensions between Israel and Hezbollah after a strike on southern Beirut killed a top commander of the armed group.

"Do Not Travel to Lebanon due to rising tensions between Hezbollah and Israel. If you are in Lebanon, be prepared to shelter in place should the situation deteriorate," the advisory said Wednesday, adding that citizens in southern Lebanon or in refugee settlements should leave.

Hezbollah has mourned its top commander Fouad Shukur, whose body was recovered from the rubble of an Israeli strike in south Beirut, as fears mounted of a wider conflict.

Shukur will be buried on Thursday and Hezbollah leader Sayyed Hassan Nasrallah will speak at his funeral to outline the Iran-backed movement's position, the group said in a statement.

Two back-to-back strikes in Beirut and Tehran, both attributed to Israel and targeting high-ranking figures in Hamas and Hezbollah, have left Hezbollah and Iran in a quandary.

Analysts agree that both strikes hit too close to home to pass without a response, and were serious security breaches for Iran and Hezbollah. Calibrating that response to restore deterrence without sparking an even more damaging escalation may be the most delicate balancing act in nearly a year of teetering on the brink of a regional war.

Israeli Foreign Minister Israel Katz has sent a letter to dozens of foreign ministers, calling on them to demand “an immediate cessation of Hezbollah’s attacks, its withdrawal to north of the Litani River, and its disarmament in accordance with U.N. Security Council Resolution 1701.”

“Israel is not interested in an all-out war,” he continues, “but the only way to prevent it is the immediate implementation of Resolution 1701.”