A police official in Nanterre said the bus was attacked on Wednesday by a gang of youths armed with a flammable liquid.
“There were at least 10 passengers on board, who only just had enough time to get out. Thankfully there was nobody with any handicaps on board, or it could have ended badly,” he told the AFP news agency.
Separately, bus routes in the Essonne area, south of Paris, were suspended because of fears of attack.
Law and order have become major issues with presidential elections due next year.
Candidates from the two biggest parties have promised a tough approach to crime.
But according to the BBC’s James Read, there has been less discussion of youth unemployment, social alienation and racial discrimination in impoverished suburban estates.