A Japanese news agency says a tape found in a video camera belonging to a staff member, who was shot dead in Myanmar, is highly likely to have been edited before being returned to his family.

Nagai Kenji was fatally shot by security forces in Yangon while he was covering a large demonstration against the military regime in 2007. His camera went missing, but it was finally returned to his family last month through a Myanmar news outlet.

Yamaji Toru, the head of the APF News that Nagai worked for, held a news conference in Tokyo on Friday.

Yamaji said the video camera was confirmed to be Nagai's as the camera's serial number matched the agency's records.

But Yamaji said he believes that footage including some from after the shooting of Nagai is missing. He made the discovery after comparing video taken by others who were at the scene.

He also said it was unlikely that Nagai filmed only five minutes of tape, pointing out that he knows Nagai's work habits.

Yamaji added that some camera parts were missing.

The agency will share the video images with the public and plans to submit the tape and the camera to Japanese police. Yamaji stressed that some questions still remained and the case is not closed.