KHARTOUM – A Sudanese woman jailed for wearing trousers deemed indecent in a landmark court case was freed on Tuesday after the country's journalist union paid a $209 fine on her behalf, the head of the media body said.

Lubna Hussein was convicted on indecency charges on Monday in a case that has attracted a worldwide outcry, and was ordered to pay a fine or face a month in jail, but was spared a penalty of 40 lashes.

Hussein, arrested at a Khartoum party in July along with 12 other women, had told Reuters after the verdict that she would refuse 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.

Mohieddin Titawi, chair of the journalist union, did not explain why his group had paid the fine. His organization is seen by many journalists as having links to the government.

Hussein's case was seen as a test of Sudan's decency regulations, which many women activists say are vague and give individual police officers undue latitude to determine what is acceptable clothing for women. Her lawyer has said he planned to appeal against her sentence.

Hussein had faced the possibility of 40 lashes for wearing trousers deemed indecent. Ten of the women arrested alongside her were flogged in July, she has said.

A former reporter working for the United Nations at the time of her arrest, Hussein has publicized her case, posing in loose trousers for photos and calling for media support.

Women have often been convicted of similar offences under Sudan's Islamic decency regulations in recent years and sentenced to beatings, Hussein's supporters say. They say she is the first to challenge such treatment.

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 have said the United Nations told Sudan that Hussein was immune from legal proceedings as she was a U.N. employee at the time of her arrest. But the case was allowed to proceed after Sudan's foreign ministry advised the court that Hussein was not immune from prosecution.

(Reporting by Andrew Heavens and Khalid Abdel Aziz; Writing by Cynthia Johnston; Editing by Janet Lawrence)