Fierce clashes are spreading through the Senegalese capital, where demonstrators are taking to the streets to protest proposed changes to the country's election laws.

VOA's correspondent in Dakar said Thursday hundreds of demonstrators took control of the main square in front of the National Assembly building, assaulting riot police with stones.

Riot police fought back, firing tear gas and water cannons, but took refuge behind the fence that surrounds the National Assembly following an hour-long battle.

Fighting has also spread to the nearby National Cathedral were oppositions protesters have fought with supporters of Senegalese President Abdoulaye Wade.

Reports from Senegal say there were also protests in the Dakar suburb of Pikine, and the central city of Kaolack.

Senegal's National Assembly is to vote Thursday on a law proposed by the ruling party that would lower the percentage of votes a winning candidate needs to avoid an election runoff. Opponents say the change would favor Mr. Wade.

The proposed law would also create a new post of vice president, which opponents believe is intended for Mr. Wade's son.

The U.S. embassy in Dakar warned Americans in the city about more demonstrations on Thursday. It urged U.S. citizens to avoid crowds, saying the protests could quickly turn violent.