MOSCOW, May 16. /TASS/. The US should firmly demand the release of Russian journalists, detained in Ukraine on Tuesday, instead of offering lenient remarks, Russian Foreign Ministry Spokeswoman Maria Zakharova said.

"Let me address my Department of State Colleagues: instead of being lenient to the Ukrainian government, which had lost any idea of human rights, demand the release of journalists in the same strict tone that you use to reproach anyone else," she said.

The Russian foreign ministry spokeswoman added she would use the same tone and language as her US colleagues if any media outlet, designated as a foreign agent in Russia, is searched.

US Department of State Spokesperson Heather Nauert has earlier told reporters that Washington took the raid on RIA Novosti Ukraine journalists in Kiev "very seriously" and urged to take such measures in full compliance with the law.

"The arrests of journalists or searches taken of media outlets, if that is done, it has to be done in accordance with the law. It is something that includes international human rights law. We take those actions seriously. We hope that the government takes those actions very seriously," she said.

"We understand that Ukraine, like a lot of other countries, has been concerned about intense propaganda," she continued. "So we do understand Ukraine’s concerns about that. But overall, these are very serious actions that have to be taken in accordance with the law."

The Committee to Protect Journalists (CPJ) expressed concern over the Ukraine Security Service's (SBU) search of the Kiev office of the Russian state news agency RIA Novosti on Tuesday and the detention of the office director, Kirill Vyshynsky.

"CPJ was unable to determine Vyshynsky's whereabouts or whether he had been formally charged," the committee said, adding that the SBU did not immediately respond to its request for more information on the case.

"We call on Ukrainian authorities to disclose the charges and evidence they have against Vyshynsky or release him without delay," CPJ Europe and Central Asia Program Coordinator Nina Ognianova said. "We also call on Ukrainian authorities to stop harassing and obstructing Russian media operating in Ukraine. The criminalization of alternative news and views has no place in a democratic Ukraine."

The Security Service of Ukraine (SBU) conducted a large-scale operation against the RIA Novosti Ukraine agency’s staff on Tuesday, accusing them of state treason. Early in the morning, office director Kirill Vyshinsky was detained near his home in Kiev. Almost immediately, the agency’s headquarters, its press center and homes of some of the employees were searched. SBU spokeswoman Yelena Gitlyanskaya said the SBU had exposed the activity of "a network of Russia-controlled media structures," which were used for "hybrid war information war against Ukraine."

RIA Novosti deputy editor-in-chief, Dmitry Gornostayev, told TASS later in the day that the chief of the RIA Novosti bureau in Kiev, Andrei Borodin, cannot be contacted and there is the suspicion he has been detained by the SBU. Later, however, he said that the agency managed to establish contact with Borodin. The reporter was not detained, but his laptop and tablet PC were confiscated, and he was summoned to SBU next week.