A lawyer sued a unit of NTT Corp. on Thursday demanding the network operator halt its plan to block access to websites that allow visitors to read pirated comics and books.

The lawyer, Yuichi Nakazawa of Saitama Prefecture, said in the first such known lawsuit that NTT Communications Corp.'s policy to block access to three sites providing hyperlinks to other sites offering pirated publications runs afoul of the Telecommunications Business Act, which guarantees privacy of communications.

NTT said Monday it will block access to the websites in line with a recent government request. A government panel decided on a tentative plan earlier this month to address internet piracy, urging network operators to voluntarily cut connections to such sites.

The move has raised concerns among legal scholars that such network access control could violate Article 21 of the Constitution, which bans censorship and guarantees privacy of communications.

According to the complaint filed with the Tokyo District Court, Nakazawa, who uses an internet service provided by NTT Communications, claims that any such move by the provider would violate his right to private communications because it would need to know the content of customers' communications to block access to the sites.

The lawyer said NTT Communications' plan lacks sufficient legal standing as there is also no provision allowing it in the contract agreement.

"It is necessary to restrict sites of pirated publications but that does not mean you can do anything," Nakazawa said. "We should have sufficient discussions for an appropriate measure, including revising the law."

NTT Communications declined to comment, saying it has not yet confirmed the complaint. It said there remains no change to its plan to block access to the sites.