By Jumana Fraije

DUBAI, July 19 (Reuters) - After Saudi police arrested a woman who appeared in an online video wearing an "indecent" skirt and crop top, many Saudis sprang to her defence on social media on Wednesday complaining that different standards were applied to men and foreign women.

Many Twitter users zeroed in on a visit to the kingdom last month by President Donald Trump whose wife Melania and daughter Ivanka were widely praised by Saudi commentators for their elegance despite eschewing veils and wearing stylish dresses.

The Saudi woman, identified only as Model Khulood, appeared on a Snapchat clip strolling through an empty mudbrick village, wearing a short skirt and a top exposing her midriff.

The online video provoked a storm of outraged commentary on social media culminating in her arrest. Her fate is not known, nor is it known if formal charges will be brought against her.

Women in the ultra-conservative kingdom are bound by law to wear robes and a headscarf, are banned from driving and require consent of a male guardian for most legal actions.

But after her detention was reported by state media, many people in the smart phone-obsessed kingdom rushed to her defense, arguing that no such scorn was piled on visiting foreign women nor Saudi men.

"If she were a foreigner, they would sing about the beauty of her waist and the enchantment of her eyes. But because she is Saudi they are calling for her arrest," Fatima al-Issa wrote on her Twitter page.

With many referring to the Trump visit, one amateur artist laboured the point of double standards by superimposing Ivanka's face on Model Khulood.

In a country in which debate is strictly policed by state decree and cultural tradition and gender mixing is often illegal, social media is one of the few outlets for young Saudis to interact and comment on current affairs.

Despite the outrage over the video, Saudis have easy access to racy imagery through the internet and satellite channels based in the kingdom which broadcast Western films.

When steamy tabloid pictures showed wealthy Saudi businessman Hasan al Jameel kissing American pop icon Rihanna in a pool last month, many Saudi men whooped in praise.

"Why is no one asking for his trial" user Noura Suliman asked querulously on Wednesday.

"Everyone's acting like a saint over just a skirt, while Hassan al-Jameel lay in Rihanna's arms and no one said a thing. Everyone praises him for that while Saudi women are being insulted," said Shajan al-Qahtani.

Others were unmoved, however, arguing that the kingdom has its own particular social codes like any other country.

"We should respect the laws of the country," a Saudi man named Faisal shot back.

"In France, the niqab (face veil) is banned and women are fined if they wear it. In Saudi Arabia, wearing robes and modest clothing is part of the kingdom's laws," tweeted one activist.

(Editing by Richard Balmforth) ((noah.browning@thomsonreuters.com;))