The United Nations has clinched a deal between Syrian stakeholders on the line-up of a committee tasked with drafting a new constitution for the war-ravaged country, the UN chief said Wednesday.

French Foreign Minister Jean-Yves Le Drian said Thursday that a claim by Yemeni rebels that they carried out attacks on two Saudi oil facilities "lacks credibility".

Israeli Prime Minister Benjamin Netanyahu called on his main challenger Benny Gantz on Thursday to form a unity government together as election results showed both without an obvious path to a majority coalition.

Netanyahu, in a video message, said he preferred to form a right-wing coalition, but the results showed it was not possible.

U.S. Secretary of State Mike Pompeo said Thursday that America backs Saudi Arabia's "right to defend itself" after a weekend attack targeted the heart of its oil industry, comments coming after he described the assault as an "act of war."

The attacks have reignited fears over a wider conflagration in the region, as tensions remain high over Iran's collapsing nuclear deal with world powers.

Kuwait's army said Wednesday it was raising its readiness levels and carrying out military exercises, amid soaring regional tensions after neighbouring Iran was accused of attacking Saudi oil infrastructure.

Iran's supreme leader Ayatollah Ali Khamenei approved last weekend's attack on Saudi Arabia's oil infrastructure, CBS News reported Wednesday, citing an unnamed US official.

US Secretary of State Mike Pompeo denounced strikes on Saudi Arabia's oil infrastructure as an "act of war", as Riyadh unveiled new evidence it said showed the assault was "unquestionably" sponsored by arch-foe Iran.

Saudi Arabia said it will unveil evidence on Wednesday linking regional foe Iran to attacks on key oil installations, as US Secretary of State Mike Pompeo heads to the kingdom to discuss possible retaliation.

Iran warned the U.S. that any action taken against it following an attack on Saudi oil installations will "immediately" be met with a response from Tehran, its state-run news agency reported Wednesday, further raising Mideast tensions.

Iran's president and foreign minister also may skip next week's high-level meetings at the United Nations as the U.S. has yet to issue them visas, IRNA reported.

Iran's President Hassan Rouhani said Wednesday Yemenis targeted Saudi oil facilities as a "warning" about a possible wider war in response to the kingdom's US-backed intervention in their conflict-ravaged country.