First reported by Nature News on Wednesday, the paper by Junjiu Huang, a gene-function researcher at Sun Yat-sen University in Guangzhou, and colleagues appears in a little known online journal called Protein and Cell.
In it, researchers describe how they edited the genomes of embryos obtained from a fertility clinic.
The embryos were non-viable, and could not have resulted in a live birth because they had an extra set of chromosomes after being fertilized by two sperm.
Researchers "attempted to modify the gene responsible for beta-thalassemia, a potentially fatal blood disorder, using a gene-editing technique known as CRISPR/Cas9," said the report in Nature News.
The researchers injected 86 embryos and waited 48 hours for the molecules that replace the missing DNA to act.
Seventy-one embryos survived, and 54 of those were tested.
Researchers found that only 28 were "successfully spliced, and that only a fraction of those contained the replacement genetic material," said the report.
"If you want to do it in normal embryos, you need to be close to 100 percent," Huang was quoted as saying.
"That's why we stopped. We still think it's too immature."
Even more concerning were the "surprising number" of unintended mutations that arose in the process, at a rate far higher than seen in previous gene-editing studies using mice or adult human cells.
Critics say the science could have unknown effects on future generations, and could open the door to a new era of eugenics by altering humans so they carry potentially desirable traits.
In reaction to the report, the Alliance for Regenerative Medicine renewed its call for a halt to the research, according to an email sent to AFP.
"Given the significant safety and ethical implications of modifying the DNA of human reproductive (germline) cells, this research is highly premature," said the statement from the international organization which represents more than 200 life-sciences companies, research institutions and advocacy groups that are focused developing therapeutics, including those involving genome editing.
"It is unacceptable to pursue this kind of research at this time. We are calling for a voluntary worldwide moratorium on this kind of research to allow for rigorous transparent legal and policy discussions and continued public debate regarding the science, safety and ethics of modifying human embryos."
At least four other Chinese research teams are believed to be pursuing similar studies, the Nature News report said.
When rumors began circulating earlier this month about the impending publication of the study, some scientists began calling for a halt to the research, while others argued that basic research should continue, to see if it may one day help cure certain diseases and disorders.
"Over the past few decades, research involving the modification of the DNA sequence in a cell has allowed scientists to investigate disease and develop new medical treatments," International Society for Stem Cell Research President Rudolf Jaenisch said in a statement, issued in response to the Chinese study on Thursday.
"However, it is too soon to apply these technologies to the human germ line, the inherited DNA, in a clinical setting, and any research involving the use of human embryos and reproductive cells should be undertaken with care and in accordance with strict ethical guidelines."