Bangkok, Thailand (CNN) FBI agents have tried to meet a pair of self-styled "sex coaches" detained in a Bangkok jail who claim to have evidence of Russian meddling in the 2016 US election, a senior Thai official told CNN.

Belarussian citizens Anastasia Vashukevich and Alexander Kirillov sent a handwritten letter last month to the US Embassy in Bangkok asking for help in getting them released in exchange for information on alleged meddling in the US presidential election.

The FBI agents contacted Thailand's Immigration bureau last week to try to organize the meeting, the highly placed source in the department said.

The request was refused by Thai officials because only legal representatives and family members of the detainees are permitted access to the detainees, added the source, who is not authorized to speak to media.

Asked about the FBI's attempt to meet the pair, a spokesperson for the US embassy in Bangkok referred CNN to a statement released last week.

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