Reports in the immediate aftermath of the crash late Tuesday suggested four Russians had been killed.
"One Russian, Galina Shvets, a guide, two Polish drivers and the wife of one of the drivers died in the road accident," the spokesman said.
Local police said around 30 passengers had been hospitalized, with 10 of them in a serious condition.
The diplomat said, referring to the group's tour operator, a total of 40 Russian men and women were in the bus. The group, comprising tourists from Moscow, the Urals and Siberia, and other areas, had arrived in the French city of Brest by train and then took a Polish bus, leased by the tour operator.
"Two trucks collided on a highway causing a 10km [6 mile] bottleneck. The bus crashed into another truck which also had failed to ease down hitting a number of cars," a local traffic police spokesman said.
The crash occurred on the Lille-Paris A1 highway near the town of Brasseuse, in the Oise region, 70 kilometers (45 miles) north of the capital, Paris.
The Russian Embassy in Paris established an emergency headquarters and a hot line following the accident. Russian diplomats contact hospitals and local officials to identify the precise number of those injured.