Two monkey-pig hybrids have been engineered in a Chinese laboratory in an experiment that has caused a stir in the scientific community.

The Chinese researchers hoped the genetic experiment would enable the growing of human organs inside animals for transplantation.

Both chimera piglets died within a week of being born, according to the New Scientist. The piglets were found to have DNA from macaque monkeys in their heart, liver, spleen, lung and skin.

Two pig-primate chimeras have been born live for the first time but died within a week. Chinese scientists are hoping to engineer pig-monkey hybrids which can grow human organs fit for transplant. (Tang Hai)

Tang Hai at the State Key Laboratory of Stem Cell and Reproductive Biology in Beijing said more than 4000 embryos were implanted in sows.

It is unclear why the piglets died, Hai told New Scientist.

The goal of Hai's team is to create healthy pigs in which one organ is composed almost entirely of primate cells.

Hai said the results brought the team "one step closer to producing tissue-specific functional cells and organs in a large animal model".

Hybrid animals have been something of a Holy Grail in some scientific circles and an ethical quandary in others.

This is not the first time hybrid animals have been engineered in a lab.

In 2010, a team of scientists at Stanford University in California, created mice with a rat pancreas.

And in 2017, researchers at the Salk Institute in California created pig-human chimeras, with around one in 100,000 cells being human. The embryos were destroyed within a month.

Salk Institute researchers faced ethical concerns over the possibility the brain of a chimera pig could be part human. That was the reason Hai's team chose to create monkey-pig hybrids.

Some scientists, such as stem cell biologist Paul Knoepfler at the University of California, doubt it will ever be possible to grow organs suitable for transplantation inside an animal-human chimeras.

However, Knoepfler told New Scientist the field should be researched further to improve tissue engineering breakthroughs.