The Senegalese President, Abdoulaye Wade, had justified the privatisation as a means of counteracting an alleged $400,000 shortfall in LONASE's funding. But protestors argued the sell-off was simply the latest in a long line of African privatisations pushed by the World Bank.
Most of the marchers were LONASE workers worried about major redundancies. According to the protest organising committee, 4000 jobs are now at risk. The demonstration was supported by trade unions, opposition parties, women's movements and NGOs.
LONASE, whose advertising slogan is 'the jackpot for the players, the benefits for the nation', pays around $1m to health and social improvement projects every year. There are fears this too could be under threat.
Senegal has already seen the privatisation of its water service (SONES) lead to price rises.
The Senegalese Social Forum, which was formed in December 2003 to challenge the imposition of neo-liberal economic policies on Senegal, is at the forefront of the protests.
The group's president, Demba Moussa Dembele, said: "Privatisation leads not just to the loss of economic sovereignty but above all to the loss of national sovereignty and [will] result in the recolonisation of Senegal."
A statement circulated by the SSF called on "all Senegalese citizens to join a patriotic show of resistance to privatisations dictated by the World Bank and the IMF."