The team also hopes to collect eggs from the last two remaining NWR females to continue the species.
Researchers used frozen sperm from male northern white rhinos - now deceased - to fertilise eggs from female southern white rhinos, a closely related sub-species, before freezing the embryos in the hope of planting them in a surrogate female southern white rhino.
This would result in hybrid embryos which can then be implanted in surrogate mothers, paving the way towards the resurrection of the northern white rhino species.
Details of their experiment are published in the journal Nature Communications on July 4.
"These are the first in-vitro produced rhinoceros embryos ever".
The key question of whether scientists can produce pure northern white rhino embryos using this technique remains unanswered. This would be achieved by adopting the procedure pioneered here, to oocytes to be collected from the last two living NWR females.
More than 20 egg collections were performed among southern white rhinos from European zoos.
To remove the eggs, the researchers patented an nearly two metre long (6.5ft) needle device guided by ultrasound. The ultrasound-guided device is placed trans-rectally.
One avenue is in vitro fertilisation with northern white rhino eggs and sperm. They are now being frozen and later will be implanted into a surrogate mother that will give birth to a hybrid offspring.
Over the past two decades, attempts at establishing a sustainable northern white rhino population - including natural breeding programs as well as artificial insemination - have been unsuccessful, according to Jan Stejskal, director of communication and global projects at the Dvur Králové Zoo in the Czech Republic, who was involved in the study.
The NWR can only reproduce in the zoos very slowly. Both animals are infertile.
The procedure for carrying out the embryo transfers is still being developed. This is why the scientists are working on an additional approach.
Of the 13 eggs injected, four developed into blastocysts (an early embryo), all of which showed signs of healthy embryonic stem cells. This would enlarge the founding genetic diversity of the future NWR population substantially. Jan Stejskal, who is a part of the research team said, "We now see clearly a moral obligation not only to help the NWR to somehow survive in captivity but later even help them get back to their original range and be wild again".
"We are quite confident with the technology we have developed", he said during a telephone conference with reporters detailing the research.
Northern white rhinos were particularly vulnerable because of conflicts that swept their central African range. All conservation efforts to save this species have been foiled by human activities such as poaching, civil war and habitat loss.
Only two of the animals remain alive, protected around the clock by armed guards on a Kenyan conservation park, and both are female.
The last male, a rhino named Sudan, died in March.
He added: "This research is groundbreaking".
Yet the use of assisted reproduction for wildlife conservation is still rare, according to a paper co-authored by Roth, having been met with a lot of resistance from within the animal conservation community. We are very thankful for all donations received from private people supporting our race against time.