The Israeli military said the head of US Central Command, General Michael Kurilla, arrived in Israel on Monday to assess the security situation as fears grow of a regional war.

Kurilla met Israeli army chief, Lieutenant-General Herzi Halevi, and "held a joint situational assessment on security and strategic issues, as well as joint preparations in the region, as part of the response to threats in the Middle East", a statement said.

The United States has deployed extra fighter jets and warplanes to the region to support Israel, as Iran and the Lebanese Hezbollah group have vowed to avenge the killings of Hamas political chief Ismail Haniyeh and Hezbollah commander Fuad Shukr last week.

Israel has claimed Shukr's killing but has remained silent on the assassination of Haniyeh, which Iran has blamed on it.

"Your arrival in Israel at this time is a direct translation of US support for Israel into action," Israel's Defence Minister Yoav Gallant told Kurilla during their meeting, according to a military statement.

"The relationship between Israel and the United States is unshakeable."

The military said Gallant and Kurilla discussed ways to "expand the international coalition facing aggressive activities by Iran and its proxies against Israel, and destabilising the Middle East".

A European diplomat in Tel Aviv meanwhile said the diplomatic community was anticipating "fairly advanced" coordination in the response from Iran and its proxies.

"That doesn't mean there will be a simultaneous response from all fronts. But in any case, it will be a coordinated response," he said, declining to be named as he was not authorised to speak on the issue.

He said efforts were ongoing seeking to tone down the rhetoric and deescalate the situation.

"All the ingredients of a Greek tragedy are present: players who don't want war but who are carried away by their own dynamics, by their own posture and by their own aggressive rhetoric, on both sides," he said.

"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."