Previously, Ukrainian Foreign Ministry spokesman Yevhen Perebyinis tweeted that Anna Duritskaya, who was with Nemtsov when the politician was gunned down late Friday, had left Moscow and was en route to Kiev.
— Yevhen Perebyinis (@YPerebyinis) March 2, 2015
"Anna Duritskaya just set out of Moscow to Kiev. Ukrainian Embassy in Moscow provided all necessary support for her return home," it reads.
He added that Duritskaya is accompanied by her lawyer.
Nemtsov was killed in Moscow at 11:40 p.m. on Friday (20:40 GMT), after four shots were fired in his back while he was walking with a female companion across the Zamoskvoretsky bridge, according to the Russian Interior Ministry.
Duritskaya said she was unaware of any threats received by the Russian politician prior to his death.
The key witness in the murder of Russian political opposition leader Boris Nemtsov, Anna Duritskaya, was not forcibly held by investigators in Moscow, the Russian Investigative Committee said Tuesday.
The Investigative Committee said Duritskaya has already returned to Ukraine and has expressed her willingness to continue her cooperation in the investigation and is prepared to appear for further questioning into the murder.
On Saturday, Russian President Vladimir Putin ordered the Investigative Committee, the Interior Ministry and the Federal Security Service to create a joint investigative team.