A masked gang have tried to abduct the daughter and young grandson of a cryptocurrency chief in Paris, but after a violent struggle, they drove off empty-handed.

The botched kidnap bid was captured on video by an onlooker in Paris's 11th district, in the east of the French capital.

Police sources said the woman was the daughter of a cryptocurrency company boss. She and her husband fought off three attackers until passers-by rushed to their aid, and the men fled in a van.

A Paris police brigade that tackles armed robbery is expected to investigate the attack, which is the latest in a series of abductions targeting French cryptocurrency figures or their relatives.

The attack unfolded at about 08:20 local time on Tuesday, according to local media, when three men leapt from a white van and tried to kidnap the mother and her child.

The pair are described as relatives of the co-founder of French Bitcoin exchange platform Paymium, the AFP news agency said.

The woman's husband who was with his family at the time tried to protect them and was beaten repeatedly over the head. The couple shouted for help as the masked men tried to pull them apart.

At one point she was seen to grab a firearm off the attacker and throw it into the street. The weapon was later described as a replica air gun.

The street was relatively busy at the time and a group of children were on their way to a local primary school.

Initially, passers-by appeared too afraid to intervene, but as locals began to react the three attackers eventually gave up and jumped into the van as a fourth gang member drove them away. One man hurled a fire extinguisher at the van as it sped off.

The family were treated for minor injuries in the hospital.

The botched kidnapping in the Rue Pache came little more than a week after French police rescued the father of a cryptocurrency millionaire who had been kidnapped in another area of the capital while walking his dog and held for ransom.

In an indication of the brutality of the gangs involved, the victim was freed three days later after his kidnappers had cut off one of his fingers.

Several people were arrested.

Last January, David Balland, co-founder of cryptocurrency wallet firm Ledger, was abducted with his wife at their home in central France.

French media say the victim had one finger missing when he was rescued from a house in Palaiseau, south of Paris.