The International Criminal Court says it is “undeterred” by Russia putting its chief prosecutor on a wanted list.
It comes two months after the ICC’s Karim Khan issued an arrest warrant for Russian President Vladimir Putin.
In a statement on Saturday, the court said the move was an attempt to undermine its “lawful mandate to ensure accountability for the gravest crimes”.
Russia, which is not an ICC member, previously described the warrant against Mr Putin as being “void”.
Mr Khan, a British lawyer, issued the arrest warrant for President Putin in March. It alleged he is responsible for war crimes, and has focused its claims on the unlawful deportation of children from Ukraine to Russia.
A warrant was also issued for Russia’s child rights commissioner Maria Lvova-Belova on similar charges.
More than 16,000 children are thought to have been forcibly transferred to Russia from Ukraine since the war began, according to officials in Kyiv.
The ICC said at the time there were reasonable grounds to believe both Mr Putin and Ms Lvova-Belova bore individual criminal responsibility.
The Kremlin’s investigative committee in turn announced this week that it would begin an investigation into Mr Khan for the “criminal prosecution of a person known to be innocent”.
In a statement on Saturday, the Hague-based ICC said it was “aware and profoundly concerned about unwarranted and unjustified coercive measures reportedly taken against ICC officials”.
Branding the measures “unacceptable”, the court said it would not be prevented from continuing to “deliver on its independent mandate”.
Mr Khan is yet to comment on the action against him.
Meanwhile, the special representative of the United Nations secretary-general for children and armed conflict, Virginia Gamba, came under separate scrutiny after she reportedly met with Ms Lvova-Belova in Moscow.
The Russian was quoted by Reuters news agency as saying the conversation was “constructive and sincere”.
Rights groups and senior officials took issue, though, with some suggesting the meeting was inappropriate.
“Ukrainian victims deserve to see Lvova-Belova behind bars in The Hague, not meeting with high-level UN officials,” Balkees Jarrah, associate director in the International Justice Programme at Human Rights Watch, said.
Last September, Ms Lvova-Belova complained that some children removed from the city of Mariupol “spoke badly about the [Russian President], said awful things and sang the Ukrainian anthem.”