All three were first hit with US sanctions after Russia annexed Crimea in 2014, and the UK sanctions will "have quite a significant impact on their ability to lead the international lifestyle that they may like to live," a Western official said.
"We have a much longer list," added the official, who asked not to be named.
"We'll be looking at those oligarchs of strategic significance and of interest to the Kremlin who are complicit by their association with the Kremlin."
British authorities have been criticised for not clamping down enough on dirty Russian money being invested in the City or luxury properties in London, earning it the name of "Londongrad".
Gennady Timchenko, 69
Timchenko is a founder of Gunvor, one of the world's largest commodity trading companies involved in oil and gas, but withdrew after US sanctions imposed in 2014.
According to the US Treasury Department, "Timchenko's activities in the energy sector have been directly linked to Putin."
Forbes estimates Timchenko's wealth at 23.5 billion dollars (euros), making him the sixth richest man in Russia.
His daughters attended British universities, at Oxford and Edinburgh.
An ice hockey fan, he has played with President Putin and remains chairman of the Russian national hockey league KHL and is president of the SKA Saint Petersburg Hockey Club.
He is also vice president of the Russian Olympic Committee.
Imprisoned Kremlin critic Alexei Navalny has said that Timchenko is one of the wealthy businessmen who paid for Putin's alleged luxurious palace on the Black Sea via shell companies.
Timchenko was also named in the investigative journalism "Pandora Papers" as having helped hide piles of cash belonging to the Kremlin's inner circle in offshore accounts.
The Rotenbergs
Boris Rotenberg, 65, and his nephew Igor, 48, are from a family that is considered very close to Putin.
They are the brother and son of Arkady Rotenberg, 70, already hit by UK sanctions.
The two brothers are childhood friends of Putin, with whom they train in judo.
Boris is the vice-president of the Russian Judo Federation, of which Arkady is the president.
They also play ice hockey with Putin, and Boris' son Roman was recently named as head coach for SKA Saint Petersburg, presided over by Timchenko, without ever having been a professional player.
Boris and Arkady got rich from state construction contracts, notably for the 2014 Sochi Winter Olympics. They were also involved with the construction of the bridge linking Russia with the Crimean peninsula after Moscow annexed the territory.
Arkady has said that he is the real owner of the Black Sea palace allegedly built for Putin.