The Saudi air force has led air attacks on Houthi rebels in Yemen, as Yemeni President Abdrabbuh Mansour Hadi left the country and arrived in Riyadh.
Iran has described the air strikes as "dangerous", while Saudi Arabia said it was "defending the legitimate government" of President Hadi.
Reports say at least 13 civilians died in air strikes in the capital Sanaa.
On Wednesday, the Saudi ambassador to the US, Adel al-Jubair, announced the beginning of the air strikes.
"We will do whatever it takes in order to protect the legitimate government of Yemen from falling," he said.
Saudi-owned Al-Arabiya TV said the UAE, Bahrain, Kuwait, Qatar, Jordan, Morocco and Sudan were sending aircraft, while Egypt, Jordan, Sudan and Pakistan were ready to take part in any ground offensive in support of the government. The US said it was providing "logistical and intelligence support".
Yemen's foreign minister calls for Gulf state intervention (24 March 2015)