Absolutely true.
They used adults as well including the elderly.
American priest John Magee took film and photographs of the tragedy. This is a 7 year old boy who was stabbed by bayonets several times perforating his stomach and abdomen. He died three days after being taken to the hospital.
There are photographs and I believe a film that exist that show infants being thrown in the air to be impaled on Japanese bayonets. I do not have access to those photographs but they do exist.
It is not a rumor, not propaganda, or lies spread by Communists, it actually happened.
The issue however, is that some Japanese today deny it happened or claim its been greatly exaggerated which makes many countries who suffered from Imperial Japanese atrocities, very upset. It would be better for Japanese government to fully disclose that the crimes were committed and those who were punished for it. Denying it, is against Japan’s best interests.