The Czech Security Information Service (BIS) said in an annual report on Friday that Russia remains interested in the Czech energy sector, particularly in any possible enlargement of Czech nuclear power plants.
"Intelligence has confirmed that Russia does not consider its ongoing interest in Czech nuclear power engineering as fighting a losing battle," the BIS said.
The state-controlled CEZ energy company scrapped a tender worth an estimated $10 billion in April 2014 to expand one nuclear power station, citing low wholesale power prices and the government's refusal to provide price guarantees for the power produced.
Ties between Russia and the European Union have been strained by the crisis in Ukraine last year, in which Moscow annexed the Crimea Peninsula and backed separatist clashes in the east of the country.
The BIS also said Russia was building a structure in Europe similar to the Comintern network used by the Soviet Union almost a century ago. Czech spy-catchers have long warned about Russian intelligence activities in the former Soviet satellite nation.
"It is assessed [by BIS] that Russia is creating a structure in Europe drawing on the concept of the Comintern founded by the Soviet Union," BIS said in the report released on Friday.
Russia's Foreign Intelligence Service declined immediate comment.
The Comintern, or Communist International — the association of local Communist parties — was established by Soviet Russia in 1919 to protect the new regime in Moscow from outside attacks.