Russia says it has blacklisted dozens of "Canadian political actors pursuing a toxic Russophobic agenda" in retaliation for Canada's decision to sanction 30 Russian officials, but is refusing to say who is on that list.

A spokesman for the Russian embassy in Ottawa confirmed on Tuesday that a "large number" of Canadians had been targeted, defending Russia's right to not release a list of names.

"We can confirm that a large number of Canadian political actors pursuing a toxic Russophobic agenda were blacklisted," said Kirill Kalinin in an e-mail to The Globe and Mail.

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"While retaining the sovereign right of disclosure, Russia will respond imminently and reciprocally in case the Canadian authorities continue playing silly and pointless 'sanctions' games."

Read more: Canada sanctions 52 human-rights violators under new Magnitsky law

Also: For son and wife of Magnitsky, Canadian law is a step toward justice for all

U.S.-born financier and anti-Putin campaigner Bill Browder said Russia is scrambling to respond to Canada's decision to target Russian officials with sanctions last week, questioning whether it had actually sanctioned anyone. Mr. Browder has led the international effort to pass legislation sanctioning human-rights abusers worldwide, in memory of Sergei Magnitsky, a Russian tax lawyer who was beaten to death by Moscow prison staff in 2009 after accusing Russian officials of theft.

"I don't think that they've sanctioned anybody because they've exhausted their list of Canadian politicians [to target] in their response to Ukraine and Crimea sanctions," Mr. Browder said.

On Friday, Russian Foreign Ministry spokeswoman Maria Zakharova said the list of Canadians prohibited from entering Russia "contains dozens of names." Her statement came hours after Foreign Affairs Minister Chrystia Freeland announced Canada's first round of Magnitsky-style sanctions, targeting 52 human-rights violators in Russia, Venezuela and South Sudan.

Asked about the embassy's comments on Tuesday, Ms. Freeland's office said it had nothing to add beyond its previous statements emphasizing that the Magnitsky law is a piece of global legislation and not aimed at any particular country.

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A senior Canadian government official said on Tuesday that Ot​tawa has not been told who may be targeted by the Russian entry ban.

Conservative Senator Raynell Andreychuk, who sponsored the Canadian Magnitsky legislation, said Russia's threat of further travel bans is a "scare tactic."

"This is a classic game – warn but no names," Ms. Andreychuk said in an e-mail.

"This means if you want to go to Russia for any reason – beware – you may not get a visa and maybe you will be vulnerable in Russia."

Ms. Andreychuk is among a group of 13 Canadian officials, including Ms. Freeland and Conservative Leader Andrew Scheer (then House of Commons speaker), Russia banned from entering the country in March, 2014, after Canada sanctioned members of President Vladimir Putin's circle over the annexation of Crimea.

Conservative MP James Bezan, also among those banned by Russia in 2014, said this isn't the first time Russia has threatened sanctions without naming anyone. He said Russia responded similarly in late 2014 when the then-Conservative government announced another round of sanctions against Russian officials, in addition to those named earlier that year.

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"The announcement from the embassy was exactly the same thing that they said just last week, which is, 'We've added a bunch of Canadians to our list. We aren't going to say who it is, but they'll find out when they try to go to Moscow,'" Mr. Bezan said.

"Is it a true retaliation? I don't know."

Last month, Canada became the fourth country to pass a Magnitsky law, giving it the power to impose asset freezes and travel bans on human-rights abusers around the world.

The legislation is named after Mr. Magnitsky, who was hired as the lawyer for Mr. Browder's Moscow-based Hermitage Capital Management hedge fund in 2005. Mr. Magnitsky was arrested in 2008 and died in prison in 2009. Investigations by Russia's human-rights council eventually concluded he was beaten to death by prison staff.

Thirty Russians were sanctioned on Friday for their involvement in the Magnitsky case. Mr. Browder said the most significant names on the sanctions list include Dmitry Klyuev, the alleged mastermind behind the criminal conspiracy that Mr. Magnitsky uncovered, and Fikret Tagiyev, the head of Moscow's Matrosskaya Tishina detention centre, where Mr. Magnitsky died.