The UEJF on Friday said that Twitter had agreed to take down many offending tweets that have recently flooded the site under the hashtag #unbonjuif (#agoodjew), with examples including: "#agoodjew is a dead Jew."
UEJF lawyer Stephane Lilti told AFP Monday that 50 new messages were sighted over the weekend using a new keyword #unjuifmort (#adeadjew).
"We are giving a few days for these tweets that we have drawn attention to be taken off," Lilti said.
A Twitter spokesman refused to comment directly on the anti-Semitic tweets and reiterated the company's standard response that it "does not mediate content."
He added, "If we are alerted to content that may be in violation of our terms of service, we will investigate each report and respond according to the policies and procedures outlined in our support pages."
These state that Twitter cannot delete tweets but allow for accounts generating content in breach of its rules or considered illegal to be suspended.
The site will not hand over details of account holders unless obliged to do so by a judge.
Last week, Twitter suspended the account of a neo-Nazi group in Germany, responding to a request of that nature from a national government for the first time.
French Justice Minister Christiane Taubira has warned Twitter that it has a duty to uphold the country's laws on racism and anti-Semitism.
The row over the tweets has blown up against a background of increasing attacks on Jews and Jewish institutions in France.
A community watchdog said two weeks ago that anti-Semitic acts had surged by 45% since the start of the year and were given fresh impetus by attacks by Islamic extremist Mohamed Merah.
Merah went on a shooting rampage in March in and around the southern city of Toulouse, killing a rabbi, three Jewish children and three French paratroopers – two of them Muslim – before being shot dead in a police siege.