Colonel Laszlo Tonhauser, head of the national police department's organised crime unit, told the agency that police grabbed the two unidentified Hungarians in a Budapest hotel car park on Monday as they sought to sell the material for $40,000 per kilogram.
Police officials could not be reached immediately to confirm the report, which said the two suspects, aged 41 and 42, had been trailed outside Hungary before the arrests.
The incident comes amid rising international concerns that nuclear material may be finding its way out of Russia to help other countries or renegade groups develop atomic weapons.
Bonn believes four seizures of illegal weapons-grade plutonium and uranium since May may have come from former Soviet stocks in Russia.
Moscow has said the source of the contraband remains to be proven but signed a pact with Germany last week to coordinate intelligence and police action to stop the deadly contraband.
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