THe BBC's Mark Doyle in Abidjan reports on Wednesday's demonstration

An Ivorian nationality certificate issued to Alassane Ouattara last month has been cancelled, in a move which could prevent him standing in presidential elections next year.

And in the capital, Abidjan, several leaders of his Rally of the Republicans party including the party's Secretary-General, Henriette Diabate, were arrested as riot police used tear gas, rubber bullets and stun grenades to disperse around 1,000 protestors.

At least two people were injured in the disturbances.

Mr Ouattara insists he is eligible to stand for president

They were demonstrating against what they charge is bias by state television against Mr Ouattara, a former prime minister who is considered the main challenger to President Henri Konan Bedie in elections due next year.

The demonstration, organised by the opposition Rally of the Republicans (RDR), had been banned by the government on Tuesday.

It began outside the national radio station, which the RDR has accused of having a pro-government bias.

Police blocked roads and dispersed the marchers, mainly young men but also women, with teargas.

Smaller throngs of youths, many wearing t-shirts and caps with party slogans, regrouped and counterattacked with stones and bottles.

In the early afternoon, about 20 RDR officials, including Mr Diabate, were bundled into several armoured police vehicles and whisked away from the party headquarters where sporadic clashes continued.

Eligibility

Mr Ouattara's supporters say President Henri Konan Bedie's government is unnecessarily harassing their leader because of the increasing threat he poses in next year's ballot.

President Bedie will stand for reeelection next year

Mr Ouattera, a former Ivorian prime minister who has held senior positions in the International Monetary Fund, is currently outside the country.

President Bedie says Mr Ouattara's father is from neighboring Burkina Faso and is therefore not eligible to stand.

Mr Ouattara insists that both his parents were born in Ivory Coast and says that he has the documents to prove it.

Forgery pressure

A judge, Zorro Ballo, who issued the Ivorian nationality certificate to Mr Ouattara says he had come under political pressure to say it was a forgery.

The BBC's Mark Doyle: Judge Zorro is seen by some Ivorians as a very brave figure

He said senior officials in the Ministry of Justice accused him of being a rebel judge and of having been promised something by the opposition leader in return for the Ivorian nationality document.

He insists that he has acted strictly within the law and that he has now revealed the political pressure on him because he feels his professional integrity is under threat.

In September, police arrested over 400 RDR supporters outside their leader's home and detained them for 48 hours.