The head of the Nato military alliance has said he is extremely concerned that tensions will escalate after an attack on Saudi oil facilities.
Jens Stoltenberg also said Iran was “destabilising the whole region”.
Earlier on Monday, the US released satellite images showing damage from the weekend's “unprecedented” strikes, which it has pinned on Iran.
Iran denies involvement, with President Hassan Rouhani calling the attack a reciprocal act by the “Yemeni people”.
Yemen's Houthi rebels – who are aligned with Iran – have claimed responsibility.
However, the US has cast doubt on their ability to carry out strikes of this magnitude and accuracy without assistance.
The Saudi-led military coalition in Yemen, which is in direct conflict with the Houthis, believes Iran provided the weapons.
“We call on all parties to prevent any such attacks occurring again because that can have negative consequences for the whole region, and we are also extremely concerned about a risk of escalation,” Mr Stoltenberg told the AFP news agency in an interview.
How unusual was this attack?
The Houthis have launched attacks on Saudi soil before, including on oil pipelines.
But this attack was on a much bigger scale, hitting the world's biggest oil-processing plant and another oil field.
