Twitter has told a Paris court it will not name an anonymous French tweeter unless a US judge orders it to do so.

Alexandra Neri, a lawyer for San Francisco-based Twitter, said the social network was bound by American law and would not divulge the information at a hearing this week.

The French Union of Jewish Students (UEJF) is suing Twitter in France to force it to unmask whoever set up the account UnBonJuif, which was used to spread anti-Semitic and racist messages in October. The French tweets used a hashtag that trended nationally in the European country until the messages were pulled.