European foreign ministers have stepped up calls for a ceasefire between Israel and Hezbollah, amid concern that Israel’s killing of Hezbollah’s longtime leader, Hassan Nasrallah, risks seriously destabilising Lebanon and the region.

Even as Israeli defence officials continued to raise the prospect of a cross-border operation into southern Lebanon, the foreign ministers of France, Germany and the UK voiced alarm over the latest escalation on the Israeli side.

Israel must “immediately stop its strikes in Lebanon”, the French foreign minister, Jean-Noël Barrot, said, adding that his country was opposed to any form of ground operation by the Israelis.

David Lammy, the UK foreign secretary, said on X that he had spoken to the Lebanese prime minister, Najib Mikati. “We agreed on the need for an immediate ceasefire to bring an end to the bloodshed. A diplomatic solution is the only way to restore security and stability for the Lebanese and Israeli people,” Lammy wrote.

The German foreign minister, Annalena Baerbock, told the broadcaster ARD that Nasrallah’s killing “threatens destabilisation for the whole of Lebanon”, which “is in no way in Israel’s security interest”.

The US president, Joe Biden, has described Nasrallah’s death as a “measure of justice”, though he also told reporters on Saturday: “It’s time for a ceasefire.”

Since Nasrallah’s death Hezbollah has said it will continue fighting Israel and has continued to fire rockets at it, including a salvo on Sunday morning.

More than 700 people have been killed in Lebanon since Israel stepped up its bombardment of of Hezbollah strongholds last Monday, according to health ministry figures.

In Beirut, displaced families spent the night on the benches at Zaitunay Bay, a string of restaurants and cafes on Beirut’s waterfront where private security usually shoos away any loiterers.

The UN refugee chief, Filippo Grandi, said “well over 200,000 people are displaced inside Lebanon” and more than 50,000 have fled to neighbouring Syria.

Nasrallah was killed in a massive Israeli air attack on Friday on Hezbollah’s headquarters in Beirut’s southern suburbs. It was a major blow to the group and to Iran, removing an influential ally who helped build Hezbollah into the linchpin of Tehran’s network of allied groups in the Arab world.

Israel announced his killing on Saturday and Hezbollah later confirmed his death.

The growing international concern over the potential impact of Nasrallah’s assassination came as Israel continued to launch dozens of strikes against Hezbollah. According to reports, one air raid in northern Lebanon on Sunday morning killed 11 people.

The Israeli newspaper Haaretz reported that the military had endorsed a potential ground operation. It cited army officials as saying they had gained substantial experience in Gaza and that Israeli intelligence on Lebanon was much better than what it had had on Hamas in Gaza.

Reports in the Israeli media suggested that the leadership of the Israel Defense Forces was continuing to push for a limited ground offensive within weeks, seeing a closing window of opportunity.

The Israeli prime minister, Benjamin Netanyahu, said on Saturday that Nasrallah’s killing was a necessary step toward “changing the balance of power in the region for years to come”.

“Nasrallah was not a terrorist, he was the terrorist,” Netanyahu said in a statement, warning of challenging days ahead.

The Israeli military spokesperson Daniel Hagari said: “His elimination makes the world a safer place.”

Hezbollah began low-intensity cross-border strikes on Israeli troops a day after its Palestinian ally Hamas staged its unprecedented attack on Israel on 7 October, triggering the war in Gaza.

The Israeli military said on Sunday that it had killed Nabil Kaouk, another top Hezbollah leader, on Saturday. Kaouk was one of the few remaining senior members of the organisation, and reportedly one of those being considered to succeed Nasrallah as leader.

Analysts suggest that Hashim Safieddine, the head of Hezbollah’s executive council, is the favoured pick to succeed Nasrallah. Naeem Qassem, the deputy secretary general of the organisation, is also reportedly in the running.

Hezbollah’s leadership has been decimated by a relentless Israeli assassination campaign.