France, Canada and Jordan were among the latest governments to issue calls for their citizens to leave Lebanon.

"In a highly volatile security context", French nationals were "urgently asked" to avoid travelling to Lebanon, and those already in the country "to make their arrangements now to leave... as soon as possible", the foreign ministry in Paris said.

The United States and Britain have issued similar warnings.

Several Western airlines have suspended flights to the region.

On Sunday Qatar Airways said that "in light of recent developments in Lebanon", the Doha-Beirut route "will operate exclusively during daylight hours" at least until Monday.

The killing Wednesday of Hamas leader Ismail Haniyeh in Tehran, hours after the Israeli assassination of Hezbollah's military chief in Beirut, has triggered vows of vengeance from Iran and the so-called "axis of resistance" of Tehran-backed armed groups.

Israel, accused by Hamas, Iran and others of carrying out the attack that killed Haniyeh, has not directly commented on it.

Haniyeh, Hamas's political chief, was the group's lead negotiator in efforts to end the war.

His killing raised questions about the continued viability of efforts by Qatari, Egyptian and US mediators to broker a truce and exchange of captives and prisoners.

Israeli ally the United States said it would move warships and fighter jets to the region to protect US personnel and defend Israel.

On April 13, Iran launched its first-ever direct attack on Israeli soil, firing a barrage of drones and missiles -- most of which were intercepted -- after a strike killed Revolutionary Guards at Tehran's consulate in Damascus.

Hamas officials but also some analysts as well as protesters in Israel have accused Prime Minister Benjamin Netanyahu of prolonging the war to safeguard his ruling hard-right coalition.

On Sunday, Netanyahu told his cabinet he was "making every effort" to return the captives and was prepared "to go a long way" to do so.