Russia demands Kiev free arrested journalist

"Russia will do everything to ensure its citizen is freed, and to prevent other journalists finding themselves in similar situations, whether they are Russian citizens or work for Russian media" foreign ministry spokeswoman Maria Zakharova said in a briefing.

Kyrylo Vyshynsky, a dual Ukrainian-Russian national who works for Russian state-run news agency RIA Novosti, was detained in Kiev on Tuesday where officials said he would be charged with treason for his "subversive" reporting to justify Moscow's 2014 annexation of Crimea.

They also said Vyshynsky later collaborated with separatist groups in eastern Ukraine, where a conflict that broke out following Crimea's seizure has cost some 10,000 lives.

The court in the southern city of Kherson, where Vyshynsky was expected to be transferred, said it had not yet received his case and a hearing may not take place until Thursday.

Zakharova accused Ukrainian authorities of a "repressive" policy against the media and expressed Russia's "indignation at the brutal violations of the freedom of the press in Ukraine".

Vyshynsky's arrest came just hours before Russian President Vladimir Putin opened a bridge providing the first direct road connection from southern Russia to the Crimean peninsula.

Vyshynsky, 51, worked for several Ukrainian media outlets before becoming a correspondent for Russia's state television channel Rossiya for several years. He later joined RIA Novosti and received Russian nationality in 2015.