Armed youths hijacked and set fire to a bus in the suburbs of Paris while hooded gangs torched two others overnight, in a flare-up of tensions on the eve of the anniversary.
Around 10 masked men, five of them carrying handguns, forced the driver and passengers off a night bus heading from Bagnolet to Montreuil, on the eastern edge of the capital, at around 1:00 am.
Both towns are in the disadvantaged, high-immigrant department of Seine-Saint-Denis, starting point of the riots that erupted on October 27 last year, spreading to hundreds of towns around Paris and other cities.
"They stole the bus, drove it a short distance away and set fire to it," a spokesman for the Paris region transport services said.
Police said that one man held his gun against the driver's head to force him off the bus, but no-one was hurt in the attack.
Earlier, hooded youths set fire to a bus in the western suburb of Nanterre, not far from the La Defense business district, leaving passengers scrambling to escape, firemen and police said.
A dozen youths boarded the bus, threw an inflammable liquid inside, lit it and fled.
"There were at least 10 passengers on board, who only just had enough time to get out. Thankfully there was nobody disabled on board or it could have ended badly," said a police officer.
A third attack took place in Athis-Mons south of Paris, where police said three masked youths ordered passengers off a bus, hurled a Molotov cocktail inside and fled.
The driver managed to put out the flames.
Officers have on several occasions been the targets of ambushes in the Paris suburbs.
Anniversary march
Mourners have marched silently through a neglected Paris suburb to mark the deaths a year ago of two teenagers that ignited three weeks of riots in largely immigrant housing projects across France.
Several hundred residents of Clichy-sous-Bois and other suburbs held a silent march in honour of Zyed Benna and Bouna Traore, teens of African descent who were electrocuted while taking refuge in a power substation from what they thought was a police chase on October 27, 2005.
Carrying a banner reading "Dead For Nothing," families of the teens led the ethnically diverse crowd away from city hall toward the power station.
A memorial will be erected at the site, which for the past year has been adorned only with the graffiti and rubble that are the signature of such neighbourhoods.
The outburst of anger at the accidental deaths of the youths, electrocuted in a power substation while hiding from police, grew into a broader challenge against the French state and its forces of order that has continued to simmer in the year since.