The airstrikes on Yemen's port of Hodeidah were in response to Houthi missile attacks on Israel in recent days, Israel said, amid fears that Middle East fighting could spin out of control and draw in Iran and Israel's main ally the United States.
The Houthi-run health ministry said at least four people were killed and 29 wounded.
The strikes took place as Israel attacked more targets in Lebanon, where its intensifying bombardment over two weeks has killed a string of top Hezbollah leaders and driven hundreds of thousands of people from their homes.
Israel on Sunday vowed to keep up its assault.
"It has lost its head, and we need to keep hitting Hezbollah hard," Israel's military chief of staff Herzi Halevi said.
Lebanon's Health Ministry said Israeli strikes on Sunday had killed 32 people in Ain Deleb in the south and 21 people in Baalbek-Hermel in the east and that 14 medics had been killed in airstrikes over the past two days.
Israeli drones hovered over Beirut overnight and for much of Sunday, with the loud blasts of new airstrikes echoing around the Lebanese capital.
Hezbollah and Israel have been trading fire across the border since the start of the war in Gaza, which was triggered by the Oct. 7 attack by Hamas militants. Yemen's Houthis have launched sporadic attacks on Israel throughout that time and disrupted Red Sea shipping.
Israel rapidly ramped up its attacks on Hezbollah two weeks ago with the declared goal of making northern areas safe for residents to return to their homes, killing much of the group's leadership. Israel's defense minister is now discussing widening the offensive.
Nasrallah's death dealt a particularly significant blow to the group which he led for 32 years, and it was followed by new Hezbollah rocket fire on Israel, while Iran said his death would be avenged.
The United States has urged a diplomatic resolution to the conflict in Lebanon, but has also authorised its military to reinforce in the region in a sign of the growing unease.
US President Joe Biden, asked if an all-out war in the Middle East could be avoided, said “It has to be." He said he will be talking to Israeli President Benjamin Netanyahu but did not elaborate.
U.S. Senator Mark Kelly, who leads a Senate Armed Services subcommittee, said the bomb that Israel used to kill Nasrallah was an American-made 2,000-lb (900-kg) guided weapon.
In Iran, which helped create Hezbollah in the early 1980s, senior figures mourned the death of a senior Revolutionary Guards member killed alongside Nasrallah, and Tehran called for a UN Security Council meeting on Israel's actions.
Iranian Supreme Leader Ayatollah Ali Khamenei was moved to a secure location in Iran after Nasrallah's killing, sources told Reuters.
LEBANESE DEATHS
Nasrallah's body was recovered intact from the site of Friday's strike, a medical source and a security source told Reuters on Sunday. Hezbollah has not yet said when his funeral will be held.
Nasrallah had not only made Hezbollah into a powerful domestic force in Lebanon during his 32 years as leader, but helped turn it into the linchpin of Iran's network of allied groups in the Arab world.
"We lost the leader who gave us all the strength and faith that we, this small country that we love, could turn it into a paradise," said Lebanese Christian woman Sophia Blanche Rouillard, carrying a black flag to work in Beirut.
Lebanon's Health Ministry said more than 1,000 Lebanese were killed and 6,000 wounded in the past two weeks, without saying how many were civilians. The government said a million people - a fifth of the population - had fled their homes.
In Beirut, some displaced families spent the night on the benches at Zaitunay Bay, a string of restaurants and cafes on Beirut's waterfront. On Sunday morning, families with nothing more than a duffle bag of clothes had rolled out mats to sleep on and made tea for themselves.
"You won't be able to destroy us, whatever you do, however much you bomb, however much you displace people - we will stay here. We won't leave. This is our country and we're staying," said Francoise Azori, a Beirut resident jogging through the area.
The UN World Food Programme began an emergency operation to provide food for those affected by the conflict.
ISRAEL MILITARY ACTION
On Sunday, Israel's military said the air force had struck dozens of targets in Lebanon including launchers and weapons stores while its navy said it had intercepted eight projectiles coming from the direction of Lebanon and one from the Red Sea.
It said dozens of Israeli aircraft including fighter jets had attacked power plants and Rass Issa and Hodeidah ports, accusing the Houthis of operating "under the direction and funding of Iran" and in cooperation with Iraqi militias.
Israeli Defense Minister Yoav Gallant said: "Our message is clear - for us, no place is too far".
Nasrallah's death capped a traumatic fortnight for Hezbollah, starting with the detonation of thousands of communications devices used by its members. Israel was widely assumed to have carried out that action but has not confirmed or denied it did.
Hezbollah's arsenal has long been a point of contention in Lebanon, a country with a history of civil conflict. Hezbollah's Lebanese critics say the group has unilaterally pulled the country into conflicts and undermined the state.
However, Lebanon's top Christian cleric, Maronite Patriarch Bechara Boutros Al-Rai, said Nasrallah's killing had "opened a wound in the heart of the Lebanese". Rai has previously voiced criticism of the Shi'ite Islamist Hezbollah, accusing it of dragging Lebanon into regional conflicts.
