Sudanese security forces have fired teargas on crowds in the centre of the capital, Khartoum.
Opposition political parties had planned a demonstration against a rise in fuel prices.
But it was declared illegal and hundreds of riot police were deployed to prevent it taking place.
Under pressure internationally to accept UN troops into its troubled Darfur region, Khartoum is clamping down on any form of internal criticism.
In the last week, the Sudanese government have arrested dozens of opposition figures.
This was a show of force from all arms of Sudan's security forces - riot police with their shields and teargas canisters, the army with guns, and everywhere plain-clothes security officers.
On each corner of central Khartoum, these men stood watching as hundreds of people ran by, clutching pieces of cloth to their faces, having had teargas fired on them.
In the back of pick-ups, more plain-clothes officers tore along the city's main street.
Wielding long sticks, they screeched to a halt at the sight of any small group gathering.
Emptying onto the pavement, these men turned on anyone who did not run.
There was little chance of a demonstration taking place.
Mounting opposition
On the face of it, this protest was about a recent rise in fuel prices.
But it is also the frontline of an increasingly bitter struggle between the Khartoum government and an alliance of opposition political parties.
Several demonstrations in the last few weeks have been banned and then violently disrupted.
What was once about fuel has turned into a question of freedom of expression.
^ Back to top | BBC Sport Home | BBC Homepage | Contact us | Help | ©
~RS~q~RS~~RS~z~RS~19~RS~)