A woman has been seriously burned and three others are suffering from smoke inhalation after youths set fire to a bus in the French city of Marseille.
| At least six buses have been set on fire in Parisian suburbs this week|
A group of teenagers reportedly forced open the doors of the vehicle and threw flammable liquid inside before fleeing.
There have been several attacks on buses over the past week, coinciding with the one year anniversary of riots in poor suburbs across the country.
The riots were sparked by the deaths of two teenagers in the capital, Paris.
Minor skirmishes were reported in Paris on Saturday. An additional 4,000 officers had been deployed - six were injured and 47 people were arrested, according to the interior ministry.
At least six buses have been set on fire in suburbs around the capital this week in an upsurge of violence ahead of the anniversary of the riots.
'Calm and dignity'
Earlier, about 500 people marched in memory of two teenage boys, both from immigrant families, who died in 2005.
Their deaths and the suggestion they had been running from police triggered three weeks of suburban clashes.
| Many youths blamed police for the teenage boys' deaths|
During the violence last year - between youths of mainly North African origin and police - more than 10,000 cars were set ablaze and 300 buildings firebombed.
The families of the two dead youths, Bouna Traore and Zyed Benna, laid wreaths at the electricity sub-station where they were electrocuted.
A monument to the boys was unveiled and the local mayor appealed for calm.
"Once again France, and even the world, is watching us and waiting to see what we do. So I appeal solemnly for calm and dignity to prevail here," said mayor Claude Dillain, quoted by the Associated Press.
But others have warned that the factors which played a key part in the riots - high unemployment, discrimination and youth alienation from mainstream society - remain unchanged.