A billionaire Saudi prince has purportedly deleted a controversial tweet in which he offered 100 luxury Bentley cars to air force pilots who took part in Saudi-led operations over Yemen.

The tweet cannot be found on the official account of Prince Alwaleed bin Talal, @Alwaleed_Talal which has more than three million followers.

He chairs Riyadh-based Kingdom Holding Co, which has interests ranging from the Euro Disney theme park to Four Seasons hotels, Citigroup and media giant News Corporation.

A purported image of his message circulated on the Internet after Twitter users said it was removed from his account.

The message congratulated the Saudi government "on the success" of the initial 27-day air campaign against Iran-backed Shiite rebels in Yemen, and on the start of a new phase which began on Wednesday.

"In appreciation of the 100 Saudi pilots taking part, it honours me to present them with 100 Bentley cars," the message said, sparking criticism from other Twitter users.

Some accused him of being a "show off," while one said a gift of 100 warplanes "would have been more patriotic".

Alwaleed's office did not respond to messages seeking comment.

No pilots died during the air campaign but eight Saudi security personnel were killed in armed skirmishes along the border with Yemen.

The World Heath Organisation says more than 1,000 people have been killed in fighting in Yemen since late March, and the UN says millions have been affected.

They are struggling to access healthcare, water, food and fuel.

In a conservative Islamic kingdom, Alwaleed, who holds no government rank, is unusual for his high profile and periodic comments about economic issues.

He is constructing a tower in the Red Sea city of Jeddah which is to rise more than one kilometre (almost 3,300 feet) to be the world's tallest building.

Earlier this year he opened a pan-Arab news channel in Bahrain but authorities there shut the station after less than 24 hours on air, in what an analyst called a worsening of press freedom.