The French government is discussing ways to increase security in the country's public transportation system, following a weekend arson attack on a bus that badly burned one woman. From Paris, Lisa Bryant reports the attack has put France on edge, a year after nationwide rioting.

Officials describe the arson attack late Saturday in the southern city of Marseille as the worst event marking a year anniversary of French riots largely staged by ethnic-immigrant youths. A group of teenagers set fire to a bus, seriously wounding a 26-year-old medical student.

French Prime Minister Dominique de Villepin is calling for all the witnesses of the bus attack to declare themselves, and said justice would be delivered and security reinforced rapidly.

Earlier, French President Chirac and other government officials telephoned the woman's family and said they would do all they could to catch and punish the perpetrators of the violence. The government has beefed up security at Marseille bus stops and established a zero tolerance policy in tough neighborhoods.

French prosecutor Jacques Beaume also said the attackers would face stiff penalties.

"Those who attacked the bus had prepared for the strike ahead of time," Beaume told French radio, "so if the act was not premeditated it at least involved preparation. The attackers could receive a prison sentence of up to 30 years, although minors would face lighter terms."

Violence by youngsters increased around the country this weekend, as France marked the anniversary of three weeks of rioting. Dozens of cars were torched and youths clashed with police in some areas. But the unrest was far less widespread than a year ago.