The normally tranquil West African state of Ivory Coast has been plunged into political tension with hundreds of supporters of an opposition party being arrested.

The unrest centres on the nationality of the opposition leader, Alassane Ouatarra, a former Prime Minister and most recently the Washington-based Deputy Head of the IMF.

His supporters were arrested while mounting a peaceful demonstration outside his house. They said the demonstration was to stop Mr Ouatarra himself being detained.

The Ivorean government says Mr Ouatarra is not Ivorean and is thus ineligible to contest presidential elections next year. Mr Ouatarra insists he is an Ivory Coast citizen.

Political row

The dispute over the nationality of Alasanne Ouatarra strikes deep into the heart of Ivorean politics and, indeed, into the very notion of the nation state in a West African region which is a patchwork of former colonial possessions.

Alasanne Ouatarra insists he is Ivorean

The government here says Mr Ouatarra hails from neighbouring Burkina Faso, on the edge of the Sahara desert, and alleges that his national identity cards may be fake.

But his supporters and many independent observers say this allegation is just an excuse by the ruling party to eliminate a wealthy and potentially powerful opponent.

Whatever the legal position, the political reality is that Mr Ouatarra's claim to Ivorean nationality is at least as valid as that of millions of immigrant workers from poor Saharan states who have lived here for generations.

Opposition leaders, and not only from Mr Ouatarra's party, say that democracy won in Ivory coast a decade ago from a dictatorial one party state is under threat.