* Al Tayyar Travel founder reportedly detained
* Top newspaper challenges businessmen to reveal source of assets
* Saudi newspaper reports no-fly list drawn up
* Purge aims to thwart opposition to reform drive - analysts
By Reem Shamseddine
RIYADH, Nov 6 (Reuters) - An anti-corruption probe that has purged Saudi Arabian royals, ministers and businessmen appeared to be widening on Monday after the founder of one of the kingdom's biggest travel companies was reportedly detained.
Shares in Al Tayyar Travel plunged 10 percent in the opening minutes of trade after the company quoted media reports as saying Nasser bin Aqeel al-Tayyar, who is still a board member, had been held by authorities.
The company gave no details but online economic news service SABQ, which is close to the government, reported Tayyar had been detained in an investigation by a new anti-corruption body headed by Crown Prince Mohammed bin Salman.
Dozens of people have been detained in the crackdown, which has consolidated Prince Mohammed's power while alarming much of the traditional business establishment. Billionaire Prince Alwaleed bin Talal, Saudi Arabia's best-known international investor, is also being held, officials said at the weekend.
The front page of Okaz, a leading Saudi newspaper, challenged businessmen on Monday to reveal the sources of their assets, asking: "Where did you get this?" in a bright red headline.
Pan-Arab newspaper Al-Asharq Al-Awsat reported that a no-fly list had been drawn up and security forces in some Saudi airports were barring owners of private jets from taking off without a permit.
Among those detained are 11 princes, four ministers and tens of former ministers, according to Saudi officials.
The allegations against the men include money laundering, bribery, extorting officials and taking advantage of public office for personal gain, a Saudi official told Reuters. Those accusations could not be independently verified and family members of those detained could not be reached.
A royal decree on Saturday said the crackdown was in response to "exploitation by some of the weak souls who have put their own interests above the public interest, in order to, illicitly, accrue money".
Analysts said the arrests were also a pre-emptive measure by the crown prince to remove powerful figures as he seeks to reshape the economy and society of the world's leading oil exporter.
Over the past year, Prince Mohammed has become the ultimate decision-maker for the kingdom's military, foreign, economic and social policies, causing resentment among parts of the Al Saud dynasty frustrated by his meteoric rise.
The round-up also targeted Prince Miteb bin Abdullah, who was detained and replaced as minister of the powerful National Guard, recalling a palace coup in June which ousted his elder cousin, Mohammed bin Nayef, as heir to the throne and interior minister.
The line between public funds and royal money is not always clear in Saudi Arabia, an absolute monarchy ruled by an Islamic system in which most law is not systematically codified and no elected parliament exists.
WikiLeaks cables have detailed the huge monthly stipends that every Saudi royal receives as well as various money-making schemes some have used to finance lavish lifestyles.
Many ordinary Saudis have praised the round-up of princes and ministers as long-awaited and needed to modernise the economy.
In September, King Salman announced that a ban on women driving would be lifted, while Prince Mohammed is trying to break decades of conservative tradition by promoting public entertainment and visits by foreign tourists.
He has also slashed state spending in some areas and plans a $300 billion sale of state assets, including floating part of state oil giant Saudi Aramco on international markets.
But the prince has also led Saudi Arabia into a two-year-old war in Yemen, where the government says it is fighting Iran-aligned militants, and a row with neighbouring Qatar, which it accuses of backing terrorists, a charge Doha denies. Detractors of the crown prince say both moves are dangerous adventurism.
The Saudi-led military coalition said on Monday it would temporarily close all air, land and sea ports to Yemen to stem the flow of arms from Iran to Houthi rebels after a missile fired towards Riyadh was intercepted over the weekend. (Writing by Stephen Kalin; Editing by Andrew Torchia and Robin Pomeroy)