Russian investigators said Saturday they had detained a man on suspicion of murder after finding the body of a foreign woman identified by media as a missing American student.
Russian news agencies identified the woman as 34-year-old US citizen Catherine Serou.
Earlier this week, investigators said that a 34-year-old foreign woman who lived just outside Nizhny Novgorod, a city some 420 kilometres (260 miles) east of Moscow, had gone missing after getting into an unidentified car.
They said she had moved to Russia in 2019 to enrol in a master's programme in law at Nizhny Novgorod's Lobachevsky State University.
On Saturday, the Investigative Committee, which probes major crimes in Russia, said it found the "missing foreign student".
"Today, as a result of a large-scale search operation, the girl's body was discovered," the Investigative Committee said in a statement, without naming her.
The committee added that police had detained "on suspicion of committing murder" a Nizhny Novgorod resident born in 1977 "who has been repeatedly convicted of grave and especially grave crimes".
Investigators said that the woman's last communication before going missing was with her mother just after 6:30 pm local time (1530 GMT) on Tuesday, telling her that she was travelling in a car with unknown people.
Search teams and volunteers had been looking for Serou in a forested area outside the city where her phone signal was last picked up.
On Friday, Serou's mother Beccy told US radio NPR from Mississippi that her daughter had moved to Nizhny Novgorod in 2019 and had sent her a final text Tuesday evening saying: "In a car with a stranger. I hope I'm not being abducted.
"And that's the last thing she wrote," said Beccy Serou, who added she had been hopeful for her safe return because she was a former US Marine who had done a tour in Afghanistan, according to NPR.
She said that her daughter had been in a rush to return to a clinic where a payment had not gone through and so may have hitched a ride with a passing car rather than waiting for her Uber.
The US embassy in Moscow confirmed the woman's death, when contacted by AFP, and said it was "closely following" the Russian authorities' enquiry.
Serou had planned on returning to the United States to pursue a career as an immigration lawyer.