One moment everything was quiet on the streets outside the Khartoum courtroom where Lubna Hussein was on trial this morning, charged with indecency for wearing trousers.

The next, a three-way fight had exploded between riot police armed with crackling electric batons, women's rights protesters waving banners and posters, and Islamists fuelled with righteous indignation and pious chants.

You couldn't have asked for a better illustration of the opposing forces that have come piling down on Sudan's government since the start of the case -- opposing forces that also compete for influence at the heart of the Khartoum regime.

Women's rights campaigners and other activists were the first to get involved after Sudan's public order police barged into a party in the capital in July and found Lubna and 12 other female guests wearing trousers.

The activists saw it as a test case for the hundreds of women who get picked up every year in Khartoum, and face flogging for a range of for public order offences, mostly related to dress. Punishments aside, may women also complain about the sporadic way the law is applied and the lack of a clear definition of indecent dress.