His departure followed intense pressure from his powerful Gulf neighbors and longtime ally Washington to step down. He had agreed to transfer power several times, only to step back at the last moment. Saleh might never return, given the opposition by large segments of the population and a powerful tribal alliance that took up arms after peaceful protests failed to persuade him to step down.

The government official, who spoke on condition of anonymity because he wasn't authorized to release the information, said Saleh had flown out of the country with most of his family. The official said he and others had only learned about Saleh's plans after the president had left.

The state-run Saudi Press Agency said Saleh arrived in Saudi Arabia late Saturday. It also said the Saudi government wished a speedy recovery to the Yemeni leader and called upon all parties to exercise restraint, noting that Yemen "risks sliding into more violence and fighting."

Washington also has expressed fears that the chaos in Yemen will undermine the U.S.-backed campaign against al-Qaida's branch in the country, which has attempted a number of attacks against the United States. Saleh has been a crucial U.S. ally in the anti-terror fight, but Washington is now trying to negotiate a stable exit for him.

The ongoing unrest has cost the government control of some remote provinces and al-Qaida and other Islamist extremists groups have exploited the turmoil to bolster their position in the country.

Yemen's constitution calls for the vice president to take over in the absence of the president, according to the official. Saleh also has been widely believed to be grooming his son, Ahmed, as a successor. Ahmed was believed to have stayed behind in an apparent bid to hold on to power.

The extent of Saleh's injuries has been a matter of intense speculation ever since the rocket struck the mosque in his presidential compound during Friday prayers, splintering the pulpit as he was surrounded by top government officials and bodyguards. Eleven guards died, and five officials standing nearby were seriously wounded and taken to Saudi Arabia.

The president delivered an audio address afterward, his voice labored, with only an old photo shown.

The Saudi king waded into the conflict after nearly four months of largely peaceful protests seeking to depose Saleh morphed into an increasingly bloody civil conflict. Past cease-fires have not held, and international diplomacy has so far failed.

Opposition tribesmen directly attacked Saleh for the first time when they landed the rockets on the mosque.

A secretary in Saleh's office and a ruling party official, who spoke on condition of anonymity because they were not authorized to talk to reporters, said Saleh spoke to the Saudi monarch afterward.

The rocket attack capped weeks of violence that erupted in the capital, Sanaa, on May 23. Residents have been hiding in basements as the two sides fight for control of government ministries and hammer one another in artillery duels and gunbattles, rattling neighborhoods and sending smoke billowing into the air.

Inspired by uprisings in Egypt and Tunisia, protesters have been trying unsuccessfully since February to oust Saleh with a wave of peaceful protests that have brought out hundreds of thousands daily in cities across Yemen.

The crisis then transformed into a power struggle between two of Yemen's most powerful families — Saleh's, which dominates the security forces, and the al-Ahmar clan, which leads Yemen's strongest tribal confederation. The confederation groups around 10 northern tribes.

Sheik Sadeq al-Ahmar, head of the powerful Hashid tribal confederation, announced his backing for the protest movement in March, but it was only when Saleh's troops moved against al-Ahmar's residence in Sanaa last week that Hashid fighters erupted in retaliation, and the battles have escalated since.