Nippon Telegraph and Telephone Corp. said Monday it will block access to websites that link visitors to sites where they can read pirated comics and books, 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 off connections to such sites.

Losses stemming from the online piracy of Japanese content such as manga, anime and music totaled an estimated ¥400 billion ($3.7 billion) in 2014, according to the Content Overseas Distribution Association, a private organization working with related industries to deal with copyright infringement.

While the government is still discussing a legal framework for regulating sites that link to pirated content, there have been concerns that such network access control could run afoul of Article 21 of the Constitution, which bans censorship and guarantees privacy of communication.

NTT's units, NTT Communications Corp., NTT Docomo Inc. and NTT Plala Inc., will block access to three sites identified by the government, Manga-Mura, AniTube! and MioMio.

The companies will cut off access to other sites if requested by the government.

"We have taken short-term emergency measures until legal systems ... are implemented," NTT said in a statement.

Two other major access providers, KDDI Corp. and SoftBank Corp., said they have not finalized their measures.