The arrests were announced on Saturday by Alexander Bortnikov, head of Russia's security service, the FSB.
"They want to make Russia dependent on their technologies," says a current FSB staffer.
His replacement, Vadim Bakatin, dismantled the secret police by splitting it into the foreign intelligence service (the SVR), and the domestic security agency (the FSB), operative today and considered by many to be the true successor to the KGB.
An Ingush official who tried to investigate the Russian security services' behaviour was himself kidnapped by the FSB.
The investigation is still open and many in British officialdom are convinced that the murder came about with the active help of Russia's FSB.
Serving or former FSB officers are unlikely to be questioned.
Russian television aired video footage of the evidence provided by the FSB, suggesting authorities in Moscow want to play up the incident.
Russia's FSB security service said in a statement it had detained Kohver in north-western Russia, close to the Estonian border, on Friday as he attempted to carry out an "undercover operation".
The police took him to the KGB's notorious Minsk prison, known by locals as the Americana (after the collapse of the Soviet Union, Russia rebranded its domestic spy agency as the FSB – Lukashenko kept the old name).
The Estonian intelligence official seized by Russia thought he was going to meet an informant in a secluded spot on the border as part of an organised crime investigation but instead walked into an FSB trap, according to Estonian security sources.
The sources said he was at the early, information-gathering stages of an investigation into a suspected smuggling operation, and noted that elements of the FSB – the Federal Security Bureau, successor to the Soviet KGB – were heavily involved in trafficking of contraband products across the European Union's easternmost border with Russia.
