* Trousers ruled indecent
* Journalists' union pays her fine
* UN rights office condemns conviction
(Adds U.N. reaction to Hussein's release)
By Andrew Heavens
KHARTOUM, Sept 8 A Sudanese woman jailed for wearing trousers deemed indecent was freed on Tuesday after the country's journalists' union said it had paid a $200 fine on her behalf.
Lubna Hussein was convicted of indecency charges on Monday in a case that has attracted a worldwide outcry. She was ordered to pay a fine or face a month in jail, but was spared a possible penalty of 40 lashes.
Hussein said after her verdict that she refused to pay the fine, preferring to go to jail instead as a means of challenging the law's legitimacy.
"They just came to me in the prison minutes ago and told me I have to go. I have no idea why. I am not happy. I told all my friends and family not to pay the fine," she told Reuters. "But I have been freed.
"I am also not happy because there are more than 700 women still in the prison who have got no one to pay for them."
Hussein's supporters say thousands of women have been convicted of similar offences under Sudan's Islamic decency regulations in recent years and sentenced to beatings. They say she is the first to challenge such treatment.
She was arrested at a Khartoum party in July with 12 other women, 10 of whom pleaded guilty to similar charges and were flogged, she has said.
Hussein however decided to fight the accusations, arguing that her "indecent" clothing, a pair of green slacks that she wore in court, were respectable and did not break the law.
Hussein, a former reporter working for the United Nations at the time of her arrest, said she believed there had been political pressure to free her and bring an end to a high-profile case.
Mohieddin Titawi, chairman of the journalists' union, said his group had paid the fine because it had a responsibility to "protect journalists when they are in prison". His organisation is seen by many journalists as having links to the government.
U.N. OFFICE CONDEMNS CONVICTION
Many women activists complain Sudan's decency regulations are vague and give individual police officers undue latitude to determine what is acceptable clothing for women. Hussein's lawyer has said he plans to appeal against her sentence.
The United Nations human rights office said Hussein's conviction violated international law.
"Lubna Hussein's case is in our view emblematic of a wider pattern of discrimination and application of discriminatory laws against women in Sudan," U.N. human rights spokesman Rupert Colville told a news briefing in Geneva.
"No defence witnesses were heard. It is not clear there is a chance to appeal," he told Reuters.
The U.N. rights office later welcomed Hussein's release but said that did not change its view that she should not have been arrested or convicted.
Hussein has said she resigned from her U.N. job to give up any legal immunity so she could continue with the case, prove her innocence and challenge the decency law.
U.N. officials had argued that Hussein was immune from legal proceedings as she was a U.N. employee at the time of her arrest. But Sudan's foreign ministry advised the court that Hussein was not immune from prosecution. (Reporting by Andrew Heavens and Khalid Abdel Aziz in Khartoum and Stephanie Nebehay in Geneva; writing by Cynthia Johnston; editing by Andrew Roche)