Former Donald Trump campaign deputy Rick Gates has been the target of an online threat by a person who invoked the Russian mafia, CNN is reporting.

Gates, who entered a guilty plea and agreed to cooperate in special counsel Robert Mueller's Russia investigation, informed a federal court of the threat on Thursday, the news network reported. His travel is restricted, but he had obtained court approval to take his family to Boston for spring break.

However, a Boston Globe story about his planned trip, "generated comments on the internet, some of which were of a threatening character," his attorney said in court papers.

CNN reported two comments, which have been taken down, referred to possible violence against Gates and suggested Russians living in Boston could by angry with him, if Mueller targeted them in the investigation.

"As a result, Mr. Gates and his wife believe it is not prudent to travel to Boston with their children," said attorney Thomas Green.

The court has approved Gates' alternative location for his family trip, but has not revealed details, the Washington Examiner reported.

Gates has pleaded guilty to one count each of conspiracy and making false statements, the Examiner noted.