Martyshev was extradited from Latvia to the US sometime in late June or early July to face charges of cyber fraud: he allegedly illegally collected private financial information from bank card holders and ran one of the largest hacker marketplaces on the dark web.
Russia takes a dim view of having its citizens prosecuted for crimes in the United States. "We consider this arrest as another case of kidnapping of Russian citizens by US authorities in violation of the current bilateral agreement on mutual legal assistance in criminal matters from 1999. The Embassy demands from the American side unconditional observance of the legitimate rights and interests of the Russian citizen," the embassy said in a Facebook post Wednesday.
The embassy said Friday that it would continue to provide all consular support to Martyshev while he was imprisoned. They also noted that the conditions Martyshev is being kept in are "normal."
The prison cell accommodates two people, according to the embassy.
Martyshev has a right to call Russia, and his relatives are expected to wire money to him soon through the embassy to make such calls, the press office noted.
A US grand jury concluded that Martyshev, along with Latvian resident Ruslan Bondar, intentionally caused damage to 10 or more protected computers in a 12-month period.
In addition, Martyshev was charged with committing wire fraud, planning to devise a scheme to defraud and aiding cyber intrusions.
Latvian authorities apprehended Martyshev and then extradited him to the United States.
On Wednesday, the Russian embassy also said that Latvian authorities had arrested Martyshev in violation of the 1999 bilateral agreement with Russia on mutual legal assistance in criminal matters.