Is it illegal in Russia to call the war in Ukraine a "war"?

Question

Several news outlets have reported that calling the Russo-Ukrainian War a "war" is illegal in Russia since a law was passed in March 2022.

Business Insider, March 2022

Putin signed a law that would punish anyone who shares "false information" about the war in Ukraine. [...] Protesters wielding "No to war!" signs in reference to the Russian invasion in Ukraine fall under the new order and could be fined up to 50,000 rubles ($448) [...]

NPR's Weekend Edition, March 2022:

Free speech and reporting may be another casualty of the Russian invasion of Ukraine, and President Putin signed a law making the airing of what the government calls false information about the armed forces illegal. Journalists could be jailed for up to 15 years. Russian officials assert it's false to call their military operations in Ukraine a war or an invasion.

However, some outlets add a qualifier such as "effectively" or "apparently" to their statements, so I'm unsure how unequivocal the law is in that respect.

Business Insider, Dec 2022

Putin signed a law in March that effectively made it illegal to call the invasion a war.

I cannot find any cases in which people have been charged with simply using the term "war" in Russia to describe the war.

Answer 1

The two facts are true. For the first see Russian fake news laws, which says the first was passed on March 4th, 2022. For the second, see Ukraine events can’t be called war, this is special military operation — Russia’s UN envoy. It's said to be "effectively" illegal to call it a war or invasion because there's probably not an official statement that combines both of these. Yet there are reports of fines and arrests happening for this very reason.

According to OVD-Info (Google translated from Russian):

For 182 days of the war, 224 people became defendants in criminal anti-war cases. On the morning of August 24, it became known about the detention of the former mayor of Yekaterinburg, Yevgeny Roizman. The politician said that a criminal case was opened against him under the first part of the article on the repeated discrediting of the Russian army because of the expression "invasion of Ukraine."

It seems to be a reliable source that is not only researching such events but also representing some of those who were arrested for various reasons. (For more information about the organization, see its Wikipedia.)

Searching more for Yevgeny Roizman, his arrest was widely publicized:

A critic of the Kremlin and former mayor of Russia's fourth-largest city was on Wednesday arrested on charges of discrediting the country's military.

Yevgeny Roizman, 59, says he was detained for calling the Ukraine war an invasion.

Moscow insists it should be called a "special military operation".

[...] Roizman told reporters he was charged under a new law adopted after Russia sent troops into Ukraine on 24 February. He faces up to five years in prison if convicted.

A Russian court ordered for Roizman to be released on Thursday but barred him from public events or communicating with anyone other than his lawyers and close family.

Russian courts fined Roizman three times earlier this year on similar charges, paving the way for a criminal case the law authorises for repeat offences.

— Euronews

It's widely believed that the laws are extremely vague so that they can be wielded to punish people who are troublesome to the Russian government when it's politically convenient, but of course there's no way to get inside their heads to prove that.

Answer 2

Yes, to the point that a St. Petersburg member of the local parliament requested Attorney General to prosecute Putin for using the word "war" in his recent speech.

Source (One of the most famous independent Russian media outlets; the original is in Russian but is quite readable with Google Translate)

As stated in his original Tweet commenting on this:

Thousands of people have already been prosecuted for such words about war

Here's a piece from a more internationally credible source - BBC. It's also in Russian. This is a Google-translated citation from one of Russian prosecutors that BBC provides:

During the inspection, it was established that publications containing unreliable socially significant information regarding the conduct of a special military operation on the territory of Ukraine were systematically placed on the Internet resource - the word "war" is mentioned everywhere on the site

EDIT

Another interesting piece. This time from RTVI (a US-based Russian media). I'm not making any claims about the credibility/biasness/independence/whatever of the source but the interesting part is this citation (the original is also in Russian as the two above):

The Russian military operation in Ukraine cannot be called a "war", since "the declaration of war presupposes the onset of legal consequences of public importance." This is stated in the objections of the Prosecutor General's Office as part of a lawsuit to recognize the illegal blocking of the Krasnoyarsk publication Krasnews.com, according to Network Freedoms (a project of the human rights group Agora*).