CAIRO -- More than 100 Saudi Arabian jets pounded Yemeni targets Thursday in a drive to stop the Houthi advance through the country, and the Saudi news media declared that the first night of the offensive had fully disabled the Houthi-aligned air force.
Iran, Saudi Arabia's regional rival and the Houthis' main ally, denounced the assault as an U.S.-backed attempt "to foment civil war in Yemen or disintegrate the country." Houthi-controlled television channels broadcast footage of dead bodies and wounded civilians, blaming "American-backed aggression."
The movement's leaders warned that the battle could widen into a regional conflict, but they also vowed to overcome the Saudi attacks without Iranian help. "The Yemeni people are prepared to face this aggression without any foreign interference," Mohammed al-Bukhaiti, a Houthi spokesman, told Reuters.
The price of crude oil spiked about 4 percent on Thursday on concerns that the fighting in Yemen might affect the passage of tankers through the Bab el Mandeb strait, a narrow chokepoint between Yemen and Africa that is the entrance to the Red Sea.
Along with Iraq, Libya and Syria, Yemen is the fourth Arab nation where an attempt to build a new democracy has been consumed by civil conflict, regional proxy wars and the expansion of extremist groups like the Islamic State and al-Qaida.
The Houthi leadership, which hails from northern Yemen, practices a variant of Shiite Islam, the religion of the Iranian theocracy. Saudi Arabia, the region's Sunni Muslim power, is backing forces loyal to President Abed Rabbo Mansour Hadi, who has fled the capital, Sanaa, and has taken refuge among his supporters in the south.
The Saudi Arabian intervention immediately raised the threat that Iran might retaliate by increasing its own support for the Houthis with money and weapons - as Tehran has in the past - or with a more active military role, escalating the violence. But the struggle for Yemen is more than merely a sectarian conflict or a regional proxy war, in part because of the singular role of the former strongman, Ali Abdullah Saleh.
Saleh left power under pressure from an Arab Spring uprising under a transitional plan brokered by Saudi Arabia and the other Persian Gulf states. As president, he fought wars against the Houthis and times appeared to ally with Saudis against Iran.
But he is a member of the same Shiite sect as the Houthis, and he has now struck an alliance with them in an apparent bid to restore himself and his family to power. He has helped lead units of the Yemeni military and security services to swing to the side of the Houthis against his successor, Hadi, and analysts say Saleh has played a much more critical role than Iran has in enabling the Houthi advance.
Some of the Houthi allies have even begun calling for the election of the former president's son, Ahmed Ali Abdullah Saleh, as Yemen's next leader. An ambassador to the United Arab Emirates and a former commander of Yemen's elite republican guard, the younger Saleh now appears on billboards around Houthi-controlled Sana urging his selection as the country's next president.
The United States and most of the Arab nations moved quickly to support the Saudi-led operation in Yemen, which Saudi Arabia has called Operation Decisive Storm.
The White House said in a statement that the United States would provide "logistical and intelligence support" to the Saudi-led military operations. "While U.S. forces are not taking direct military action in Yemen in support of this effort, we are establishing a joint planning cell with Saudi Arabia to coordinate U.S. military and intelligence support," Bernadette Meehan, a spokeswoman for the National Security Council, said in a statement.
"The United States strongly condemns ongoing military actions taken by the Houthis against the elected government of Yemen," she said.
"We strongly urge the Houthis to halt immediately their destabilizing military actions and return to negotiations as part of the political dialogue," she said, adding, "The violent takeover of Yemen by an armed faction is unacceptable and a legitimate political transition - long sought by the Yemeni people - can be accomplished only through political negotiations and a consensus agreement among all of the parties."
Four other Persian Gulf monarchies, Bahrain, Kuwait, Qatar and the United Arab Emirates, joined the Saudi operation, as well as the allied Arab kingdoms of Jordan and Morocco.
Egyptian state news media reported that Cairo was also providing undefined political and military support. The Egyptian government was consulting with Saudi Arabia about the possibility of providing forces in the naval or air support or ground troops as well, the state news media reported.
Of the Persian Gulf states, only Oman declined to participate. Two other less expected nations outside the immediate region - Pakistan and Sudan - took part as well, according to the Saudi-owned Al Arabiya network.
Al Arabiya reported that in addition to 100 fighter jets, Saudi Arabia had deployed 150,000 soldiers and other naval units. But the operation has so far consisted only of an aerial campaign.
Residents of Sanaa, the Houthi-controlled capital, said the airstrikes hit the al-Dailami air base and the international airport. Anti-aircraft gunfire continued for hours, and residents said they saw flames rising from both facilities.
By morning, local health officials said 25 people had died and 40 others were wounded, and the Houthi-controlled state television channel urged anyone with medical training to rush to the city's hospitals.
Many residents were packing up to leave the city, some of them forced out because their mud-built houses had collapsed from the bombing.
"Sana is not safe anymore; we are leaving for our village," said Mohammed al-Wesabi, walking with his wife and three children and carrying their luggage.
Usually busy streets were largely deserted, and schools and universities were closed. But some making their way to work said the strikes had increased support for the Houthis.
"Though I don't agree with the Houthis in many aspects, this airstrike against our homeland is a war against us in all," said Wahib Sharabi, 29, a civil engineer. "It's the beginning of the end of the Saud House."
The Iranian deputy foreign minister for the region, Hossein Amir-Abdollahian, told Iranian state radio that "some parties are either trying to foment civil war in Yemen or disintegrate the country." Speaking on a visit to Moscow, he said, "We believe that a national dialogue should take place in the historical capital of the country Yemen at the earliest; and in the framework of a political process, peace and stability will be restored."
The whereabouts of Hadi, the Saudi-backed leader, were unknown on Thursday. He had fled last month to the southern port city of Aden but slipped out of public view on Wednesday when the Houthi forces appeared to close in on the city.
Riad Yassin, Yemen's foreign minister, said on a Saudi-owned television station that Hadi's government applauded the airstrikes.
"I hope the Houthis listen to the sound of reason," he said, according to The Associated Press. "With what is happening, they forced us into this," he said.
In Aden, residents said on Thursday that clashes between militias supporting him and forces allied with the Houthis had broken out in several districts, including near the city's airport and the Bader military base.
"I can hear loud explosions near the airport and the base," one resident said in a telephone interview, speaking on the condition of anonymity for fear of attracting the attention of fighters on either side.