It has been established that Evikova arrived in Pyatigorsk in May and planned to take a car to Nazran, Ingushetia (a North Caucasus republic neighbouring Chechnya), on June 1.
"However, an unidentified man phoned the Prague HQ of the organisation twice on July 1 and July 4 to say that the Slovakian citizen was on Chechen territory," the source said.
He demanded a ransom of $1 million for the release of the woman.
Earlier, the Russian Foreign Ministry said that the Slovakian ambassador to Moscow, Augustin Cisar, had requested the Russian authorities' assistance in the search for the missing Slovakian citizen. In this connection, Russian Deputy Foreign Minister Sergei Razov met the ambassador.
According to the Slovakian media, the 28-year-old woman set off from Pyatigorsk to Ingushetia on May 26 to visit her acquaintances. The contact with Evikova was lost on June 1.
Her Ingush acquaintances reported about her disappearance on June 8. The spokesman for the Slovakian embassy told the Slovak TASR agency that OPU where Evikova worked had asked the embassy for help in the search.