Hostilities also threatened to expand to Yemen after the United States and its allies jointly warned the country’s Houthi rebels of unspecified consequences unless they immediately halted attacks on Red Sea shipping carried out in solidarity with Hamas.

“I would not anticipate another warning,” AFP quotes a senior US official as saying, calling the message “very clear”.

Washington has rejected suggestions of either its or Israel’s involvement in the Iran twin explosions.

But a US official told AFP that an unclaimed strike the night before that claimed the life of Hamas’s number two in a Beirut suburb had been the work of Israel.

In a visit on Wednesday to the Lebanese border, where Israeli forces have regularly traded fire with Iran-backed Hezbollah, Israeli army chief Herzi Halevi said troops were “in very high readiness”.