French investigators have issued a request for the extradition of a Chilean man suspected of murdering his Japanese ex-girlfriend in the eastern French city of Besancon in December 2016, the prosecutor leading the probe said Thursday

Narumi Kurosaki, 21, went missing from her university residence in Besancon, a town near the Alps, after having dinner with her Chilean ex, Nicolas Zepeda, 28.

Investigators are convinced that Kurosaki was killed by Zepeda in a jealous rage but her body was never found despite extensive searches.

Laying out the findings of the 34-month probe, Besancon prosecutor Etienne Manteaux said he hoped Zepeda, a teaching assistant, could be brought to trial in France.

He said his office had sent a request for Zepeda's extradition to the French government, to be formally presented to Chile.

But he acknowledged that it faced "numerous obstacles", with Chile generally loathe to hand over its nationals for trial abroad.

If Santiago refused the request, Zepeda will be tried in absentia, which would "obviously be unsatisfactory," Manteaux said.

Kurosaki disappeared on the night of December 4. She was last seen dining with Zepeda at a restaurant a short drive from Besancon.

In the early hours of the following morning, fellow students heard cries and thuds coming from the area of her room but her disappearance was not reported for several days, by which time Zepeda had returned to Chile.

France issued an international warrant for Zepeda's arrest but a Chilean judge in February 2017 rejected the request to arrest him, citing insufficient evidence.

French investigators believe Nicolas Zepeda, seen here in 2017, killed his ex-girlfriend in a jealous rage
French investigators believe Nicolas Zepeda, seen here in 2017, killed his ex-girlfriend in a jealous rage AFP / Pablo VERA

The suspect was questioned on April 18 by a Chilean judge in the presence of French investigators, including Manteaux. Zepeda denies any hand in Kurosaki's disappearance.

Zepeda, who had threatened Kurosaki in a video posted online which he later removed, admits going to her room on the night of her death for what he described as consensual sex and says he left straight afterwards.

No blood was found inside Kurosaki's room when police searched it 10 days later.

Soil found in car

Investigators suspect that Zepeda, who had questioned a doctor cousin of his about the principles of suffocation, strangled his ex.

The pair met in 2014 in Japan, where Zepeda was a student, and a year later began a relationship that ended after Kurosaki moved to France in August 2016.

In Besancon, Kurosaki entered a new relationship, a development which "clearly exasperated Nicolas Zepeda", according to Manteaux.

In the days before her disappearance, Zepeda flew to France, hired a car and drove to Besancon, stopping on the way to buy matches, flammable liquid and bleach at a supermarket.

When he returned his hire car three days after Kurosaki's disappearance, it was "very dirty" with soil found on the driver's side and in the trunk, Manteaux said.

For several days after her disappearances, messages continued to be sent from Kurosaki's phone to her friends and family, including messages in Japanese.

A Japanese friend of Zepeda told police he had asked her to translate sentences into Japanese, which later appeared in one of the messages sent from the missing woman's phone.