A citizens' group charged Wednesday that the government pressured organizers of an international security conference to cancel a lecture by an American computer expert who performed a security audit on the government's online resident registry network on behalf of Nagano Prefecture last year.

The group supporting lawsuits to suspend operation of the network, known as Juki Net, said in a statement, "The Internal Affairs and Communications Ministry cowardly suppressed free speech in an attempt to block a move to show Juki Net is full of flaws."

The group is led by Chuo University professor emeritus Narihiko Ito, Sophia University media law professor Yasuhiko Tajima and five other university professors.

The American computer security expert, Ejovi Nuwere, whose autobiography is titled "Hacker Cracker," conducted the experiment on Juki Net for Nagano Prefecture and said the prefectural government can alter private information in the system.

He was scheduled to speak at a seminar on information security held Nov. 12 in Tokyo Friday that drew around 160 security experts from eight countries.

Nuwere said on his Web site, however, that the Japanese government prevented him from speaking at the PacSec security conference.

The ministry "prevented my talk by threatening the Japanese . . . who currently are seeking contracts from the government," he said.

When asked about the accusations, one ministry official said: "We have requested that (the engineer) refrain from exposing specific vulnerable points of the system. We have not heard anything about the cancellation from the organizers (of the seminar)."

Under the network, which was launched in August 2002, each resident is identified by an individual code and personal details, including name, address, date of birth and sex, that are registered by municipalities, via prefectural governments, in a database run by the central government.