Saudi Arabia launches air strikes in Yemen
Saudi jets targeted Houthi positions in the capital Sanaa overnight, along with missile batteries and warplanes.
Mr Hadi fled to an undisclosed location after rebel forces neared his refuge in the southern city of Aden on Wednesday.
A Houthi official warned the coalition that it risked provoking a wider war.
Shia power Iran, which Sunni-ruled Saudi Arabia accuses of backing the rebels, also demanded an immediate halt to the strikes, which it said violated Yemen's sovereignty.
"We will make all efforts to control [the] crisis in Yemen," Iranian Foreign Minister Mohammad Javad Zarif said, according to the Isna news agency.
A conflict that pulls in regional powers could disrupt global oil supplies, and the price of Brent crude rose almost 6% after the strikes began.
Homes destroyed
The Saudi ambassador to the US announced the start of "Operation Storm of Resolve" at a news conference in Washington on Wednesday night.
Adel al-Jubair said it would begin with air strikes, but vowed: "We will do whatever it takes in order to protect the legitimate government of Yemen from falling."
Saudi-owned Al-Arabiya TV reported that 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. Oman is the only Gulf Arab state not participating.
The US said it was providing "logistical and intelligence support".
As Mr Jubair spoke, huge explosions were heard in Sanaa, as warplanes attacked the al-Dulaimi air base near the international airport and other locations. Rebel fighters responded by firing anti-aircraft guns and missiles.
Security officials told the Associated Press that the targets included a missile base controlled by the Houthis, as well as a nearby fuel depot. A camp for a US-trained special forces unit loyal to ousted former President Ali Abdullah Saleh, who is backing the rebels, was also hit.
BBC
