Not sure if serious. The only other guy I know calling these “partisans” is Ponomarev:
A former member of Russia’s Duma who was expelled for anti-Kremlin activities has claimed that Russian partisans were allegedly behind a car bomb which blew up the daughter of one of Vladimir Putin’s close political allies on the outskirts of Moscow.
Speaking in Kyiv, where he is based, Ilya Ponomarev alleged the explosion on Saturday evening was the work of the National Republican Army, which he claimed was an underground group working inside Russia and dedicated to overthrowing the Putin regime.[…]
“This action, like many other partisan actions carried out on the territory of Russia in recent months, was carried out by the National Republican Army (NRA),” Ponomarev said. He was speaking in a 7pm broadcast on February Morning, a Russian-language opposition TV channel he launched in Kyiv earlier this year.
He added: “A momentous event took place near Moscow last night. This attack opens a new page in Russian resistance to Putinism. New – but not the last.”[…]
This is from a Guardian article a few months ago:
Ex-Russian MP claims Russian partisans responsible for Moscow car bomb | Russia | The Guardian
Americans seem to disagree:
U.S. officials said the drone attack on the Kremlin earlier this month was likely orchestrated by one of Ukraine’s special military or intelligence units, the latest in a series of covert actions against Russian targets that have unnerved the Biden administration.[…]
In addition to the drone attack, U.S. officials say they believe the Ukrainians were responsible for the assassination of the daughter of a prominent Russian nationalist, the killing of a pro-Russian blogger and a number of attacks in Russian towns near the border with Ukraine, the most recent of which occurred Monday.[…]
This is from a NYT article from a week or so ago:
Ukrainians Were Likely Behind Kremlin Drone Attack, U.S. Officials Say
On this note, the same article suggests the following:
U.S. intelligence agencies do not know which unit carried out the attack and it was unclear whether President Volodymyr Zelensky of Ukraine or his top officials were aware of the operation, though some officials believe Mr. Zelensky was not.
And an article at the WP from yesterday suggests that Kiev may have no control of how the supplied weapons are being used, which is probably highlighted by recent statements from the State Department and other entities from other countries that they are not encouraging or supporting the attacks on Russian territory (to the point that the weapons are supplied on the condition that they are not to be used in Russia), as well as public statements from Ukrainian officials that they are “prohibited” to do so with the western supplied weapons.
[…]U.S. and Western officials have insisted that Ukraine carefully track the billions of dollars’ worth of weapons that have flowed into the country. Kyiv’s backers have also largely barred Ukrainian forces from using Western weapons and equipment for attacks on Russian soil. Yet the recent raid into Russia underscores how materiel can change hands in unpredictable ways, creating oversight challenges that few in Washington and Kyiv appear willing to acknowledge.[…]
The WP article:
https://www.washingtonpost.com/national-security/2023/06/03/nato-weapons-russia/
So “partisans” is a quite a bit of a stretch.