Manager Christelle Simon said four men, heavily armed and with faces covered, burst in and fired shots in the air just after 2:00 am (0100 GMT) and jumped into a getaway car three minutes later after stealing "almost nothing."

"They wanted to get into the safes but one of the managers told them it was impossible because they have time locks," Simon told AFP. A police source who asked not to be named said the loot totalled about 7,000 euros ($9,500).

About 20 staff and a few dozen gamblers were in the seaside casino at the time. One cashier got a punch on the cheek and another employee was bashed on the head with the butt of a gun. No customers were harmed.

Police said later on Tuesday they had arrested a total of eight people in connection with this and two earlier casino robberies in northern France. Seven such robberies have been reported in France in 10 months.