The scene, in a YouTube spoof video satirising a new state agency to combat corruption, has attracted 2.2 million viewers in a strait-laced Islamic kingdom where Saudi online comedians are tackling once-taboo subjects - and gaining a wide following.

Another video satirises a prince for mishandling anti-corruption demonstrations, while mobile phone footage of the so-called morality police harassing a family in a shopping mall went viral this year with over 180,000 hits.

The overall impact of such vignettes cannot be measured, but in Saudi Arabia, where around 70 percent of the population is under the age of 30, and where Internet penetration is around 40 percent, social media are driving public debate on a host of subjects that were once seen as strictly off-limits.

"(Our) team is very careful not to cross the red lines and instead reflects all the issues that have caused controversy or debate that have been discussed in the media," said Lama Sabri, a writer for "Aaltayer", which translates roughly as "On The Fly", one of the popular YouTube shows.

"The programme also uses comedy to make fun of the existence of these red lines," she added.

Saudi Arabia is a monarchy with no elected parliament, where the most senior positions are occupied by high-ranking royals, some of whom also have extensive business interests.

The media is censored and reporters who cross unofficial red lines can face the sack, hefty fines or even prison sentences.

But bloggers and contributors to online forums now openly discuss social ills, government inefficiency and corruption, while a Twitter user who ridicules the royal family has attracted 250,000 followers.

"The Internet has always provided a space for Saudis to express themselves freely in unprecedented ways, and this (Twitter) is just the latest platform," said Ahmad al-Omran, a well-known Saudi blogger. "People are becoming more vocal and critical on Twitter."

Social media helped to catalyse the political unrest that convulsed many Arab countries last year, mobilising street protests that overturned regimes and led to mass insurrection across North Africa and the Middle East.

Saudi Arabia, where the king is broadly popular, escaped that surge of public anger and analysts say the growth of more forceful debate is unlikely to send crowds into the streets.

SATIRE AND PARODY

But government officials are being skewered online, in comic films and other formats, as never before.

One film mocking the Commerce Ministry for perceived double standards in enforcing business regulations attracted more than 915,000 hits on YouTube. Small traders must stick to the letter of the law, it suggested, but powerful businessmen can get away with selling the public that rarest of commodities: air.

Not all the criticism comes in comic or satirical guise.

More than 52,000 people have viewed a film commemorating victims of Jeddah's deadly 2011 floods by showing notional "corpses" wrapped in blue sheets in the worst-hit areas.

Many Jeddah residents blamed the disaster on the government's failure to erect proper flood defences.

Countless Saudis have seen the mobile phone footage of the morality police accosting a family out shopping. King Abdullah later sacked the head of the religious organisation dedicated to enforcing its vision of Islamic behaviour.

On Twitter, an anonymous writer using the pseudonym "Mujtahidd" has amassed a huge following with a series of detailed posts about the alleged misdeeds of members of the extensive royal family.

The writer accused one senior royal of bullying a judge into helping him perpetrate property fraud by forging documents, and denounced another for stock market manipulation.

"I believe that exposing corruption on its real scale is a very effective way of convincing people to move against it," Mujtahidd said in an email to Reuters.

The tweets have gained such notoriety that the Grand Mufti, without referring to Mujtahidd directly, launched his own attack on Twitter last month, saying the social network "promotes lies" and includes "attacks against religious and society figures".

ESTABLISHMENT CONCERNS

While politically engaged Saudis are by turns thrilled and scandalised by the uncontrollable nature of online debate, the establishment has shown it is worried.

A law introduced last year made blogs and other social media subject to some of the same restrictions as conventional media.

"I enjoy reading Mujtahidd's tweets, but it's dangerous because he's attacking these very prominent people without any sort of evidence and hurting public confidence in the state," said one prominent Saudi.

The example of Hamza Kashgari, a young blogger who may face trial after being extradited from Malaysia for allegedly blasphemous posts about the Prophet Mohammad, is a stark warning of what can happen when online comments outrage public opinion or upset the authorities.

Some Saudis believe the greater public scrutiny that social media allows is making a mark as more senior officials and royal family members take note and join online discussions.

Prince Talal bin Abdulaziz, the half-brother of King Abdullah, and Information Minister Abdulaziz Khoja are among the most senior Saudi personalities to join Twitter.

"Definitely the government is paying attention and monitoring... The number of subscribers on Twitter in Saudi is among the highest in the region so it is being looked at with some seriousness," said Hussein Shobokshi, a Saudi analyst.

"It will be one of the things that we will see growing to have more and more influence," he added. (Writing by Angus McDowall; Editing by Alistair Lyon)

• A Permanent Economic Emergency