A Saudi columnist has triggered a furore in the ultra-conservative kingdom after he wrote on micro-blogging website Twitter that some Saudi women were working as prostitutes in Dubai. Dubai, in the neighbouring United Arab Emirates, is the most liberal city in the Gulf and hundreds of thousands of Saudis flock there for holidays or weekend breaks. \"Some Saudi women are working as prostitutes in Dubai,\" tweeted Mohammed al-Sheikh, who also writes a column in the Al-Jazeera newspaper. His comments last week have sparked a storm of protest on Twitter, particularly from conservative Muslims, with some calling for an apology and others demanding that he be prosecuted. An influential cleric active on Twitter, Sheikh Nasser al-Omar, said: \"Whoever insults a Muslim must be judged according to sharia (Islamic law). Who is he to insult women of a pure country?\" Another preacher, Ghazi al-Shammari, announced that he would go to Dubai next week \"to provide evidence of these lies.\" Sheikh responded by saying that his remarks had been misinterpreted but has refused to apologise. For millions of Saudis, social networks are a rare bubble of freedom in the kingdom, with more than 100,000 people active on Twitter and 4.5 million Facebook users. In February, a young Saudi journalist, Hamza Kashgari, had to flee the country after having made remarks on Twitter that were deemed blasphemous and earned him death threats. He was arrested in Malaysia and sent back to Saudi Arabia, where he has been detained. He later published a poem on Twitter expressing his repentance.