Russia's Foreign Ministry said it would retaliate and its response would be painful for Hungary, Interfax news agency reported.
Orban, swept from power in Hungary in April after 16 years in office, had kept close ties with Russian President Vladimir Putin even after Russia invaded Ukraine in February 2022.
Under him, Hungary continued buying Russian oil and gas, held up European Union sanctions on Russia and blocked a 90 billion euro ($A134 billion) EU loan to Ukraine.
After Russia invaded Ukraine, many European countries expelled dozens of Russian diplomats, while Hungary expelled none. Until Tuesday, it had not sent any home publicly since 2018.
Those kicked out "were engaged in activities in Hungary that are unacceptable for diplomats under the Vienna Convention," Hungarian Foreign Minister Anita Orban, who is not related to the former prime minister, said in an emailed statement.
"This decision ... does not imply breaking off diplomatic relations with Russia. Hungary intends to continue the necessary dialogue," the statement added.
New Prime Minister Peter Magyar and his centre-right government have repeatedly said Hungary's main alliances are the European Union and NATO and the government aims to rebuild trust eroded under Viktor Orban.
In a parliamentary hearing in May, Anita Orban said Russia would "remain a partner" but the relationship could not be based on "one-sided dependency," adding that Russia's policies pose a security challenge to Hungary and Europe.
