The United States announced that it is working tirelessly to prevent a full-scale war in the Middle East, as Israel remained on high alert Tuesday for potential Iranian retaliation following two high-profile killings. US President Joe Biden, whose country has deployed additional warships and fighter jets to the region in support of Israel, conducted crisis talks on Monday with his national security team. Biden and his top diplomat Antony Blinken aimed to ease tensions that have escalated since a suspected Israeli attack in Tehran last Wednesday resulted in the death of Ismail Haniyeh, the political leader of Palestinian militant group Hamas.

Biden contacted King Abdullah II of Jordan, which assisted in downing Iranian drones and missiles during an attack on Israel in April, while Blinken reached out to high-ranking officials in Qatar and Egypt, key intermediaries seeking a ceasefire in the 10-month Israel-Hamas war in Gaza. "We are engaged in intense diplomacy, pretty much around the clock, with a very simple message -- all parties must refrain from escalation," Blinken stated after a White House meeting with other top officials. Iranian President Masoud Pezeshkian condemned what he described as Israel's "criminal acts" against the "oppressed and defenceless people of Gaza" and Haniyeh's killing.

"The Islamic Republic of Iran is not seeking to expand the scope of war and crisis in the region, but this regime will undoubtedly receive the response for its crimes and arrogance," Pezeshkian said during talks with a senior Russian official, according to the official news agency IRNA. The killing of Haniyeh, which Israel has not directly acknowledged, occurred shortly after an Israeli strike in Beirut killed the military chief of Lebanon's Hezbollah movement, Fuad Shukr. Israel held Shukr accountable for a rocket attack in the annexed Golan Heights that killed 12 children, labeling him as Hezbollah chief Hassan Nasrallah's "right-hand man."

Nasrallah was scheduled to deliver a speech Tuesday marking one week since Shukr's death. His Iran-backed group has been involved in near-daily cross-border clashes with Israeli troops since Hamas attacked Israel in early October. On Tuesday, four Hezbollah fighters were killed in an Israeli strike in southern Lebanon, according to a security source. A European diplomat in Tel Aviv anticipated a "coordinated response" from Iran and its proxies but noted that de-escalation efforts continued.

"That doesn't mean there will be a simultaneous response from all fronts," he added, declining to be identified as he was not authorized to speak on the issue. "We're telling them they have to stop playing with fire, because the risk of flare-ups is higher than at any time since October 7," he said. Turkey joined multiple governments in urging its citizens to leave Lebanon, where Hezbollah is based, while China advised increased caution. Numerous airlines have suspended flights to Lebanon or restricted them to daylight hours.

Lebanese national carrier Middle East Airlines added extra flights for people wishing to leave or return, according to a company source. As tensions escalated, the Jeddah-based Organization of Islamic Cooperation is set to meet on Wednesday at the request of "Palestine and Iran" to discuss regional developments, an OIC official said. The head of the US military command covering the Middle East, General Michael Kurilla, arrived in Israel on Monday and met with military chief Lieutenant-General Herzi Halevi for a security assessment, according to an Israeli statement.

Iraqi sources reported that a base hosting US troops in Iraq was targeted by rocket fire on Monday, following an American strike on July 30 that killed four pro-Iran Iraqi fighters. The United Nations' rights chief Volker Turk urged "all parties, along with those states with influence, to act urgently to de-escalate what has become a very precarious situation". Italian Foreign Minister Antonio Tajani and his Iraqi counterpart Fuad Hussein agreed in a joint statement Monday to make every effort to avoid a regional escalation. Italy currently holds the rotating presidency of the G7 group of countries.

The Israel-Hamas war in the Gaza Strip, initiated by the Palestinian group's October 7 attack on Israel, has involved Iran-backed militants in Syria, Lebanon, Iraq, and Yemen. The Hamas attack led to the deaths of 1,197 people, mostly civilians, according to an AFP tally based on Israeli official figures. Palestinian militants captured 251 hostages, 111 of whom remain held captive in Gaza, including 39 the Israeli military claims are dead. In Tel Aviv on Monday, thousands of Israelis gathered to commemorate the fifth birthday of child hostage Ariel Bibas and to demand the release of him and his family.

Israel's retaliatory military campaign in Gaza has claimed the lives of at least 39,623 people, according to the Hamas-run territory's health ministry, which does not provide details on civilian and militant deaths. In the occupied West Bank, Palestinian officials reported that Israeli forces killed eight people in two separate raids on Tuesday.