Russian authorities quickly blamed Ukraine for the car bomb that killed a Russian journalist last weekend, but intelligence experts say that although Kyiv is capable of orchestrating such an attack, the prospect is unlikely.

Daria Dugina, 29, who died Saturday outside Moscow, was the daughter of ultranationalist Alexander Dugin, a vocal supporter of the Ukraine invasion launched by President Vladimir Putin six months ago.

Kyiv has rejected the claim by Russia's FSB security services that the killing was the work of a Ukrainian woman sent to track and eliminate Dugina, who later fled to Estonia.

"Could we get 400 grammes [just under a pound] of TNT into Russia? In theory, yes. Could we set a bomb? Yes," a high-ranking member of Ukraine's intelligence service told AFP on condition of anonymity.

"But the big problem is, what good would it do? Nobody in Ukraine even really knows about Dugin. Who would have something against his daughter? Killing her makes no sense," the source said.

Since Russia's seizure of the Crimean peninsula in 2014, Ukraine has effectively been waging a clandestine war against Russia, building out spy networks in preparation of future tensions.

"I think that since March there are Ukrainian logistical and operational networks in place in Russia... There are Ukrainians on the other side of the border," said Gerald Arboit, an international intelligence expert at the CNAM research institute in Paris.

However, "For this type of attack you'd need reconnaissance, to follow her, and then call in a team to carry it out -- you'd need two or three people to booby-trap a car -- one person alone couldn't do it all," he said.

He did not dismiss Ukrainian involvement, possibly with domestic Russian opposition groups, noting that Russia's FSB security services had dismantled Ukrainian networks in recent years.

Getting Ukrainian agents into Russia would also require eluding Russian intelligence agencies presumably on high alert after six months of war.

"The assassination of Dugina took place in Moscow, which would be an incredibly hard target for the Ukrainian services to penetrate," said Colin Clarke, research director at the Soufan Center in New York.

"But at the same time, I think it could be possible... elite Ukrainian special forces or intelligence assets are likely capable of pulling off the attack," he said.

Experts also noted that Dugina's killing would most likely serve Putin's interests, fomenting anger that could bolster support for a general mobilisation to muster more soldiers for a war that has largely stalled in Ukraine's south and east.

"I don't rule out that Dugina was killed by the Russians to step up the Ukraine war, potentially with non-conventional weapons" such as thermobaric bombs, said a French intelligence source contacted by AFP.

Targeted assassinations of high-profile Russian targets, particularly a young woman, would also be counter-productive for Ukraine's President Volodymyr Zelensky, who is banking heavily on sympathy and military aid from Western allies.

"I don't see the rationale of such an operation for the Ukrainians, which would be very complex to carry out," said Alexander Grinberg, an analyst at the Jerusalem Institute for Security and Strategy.

"And I can't imagine the Americans or British letting them do it," he added. "It seems like an FSB ploy to undermine Kyiv, especially since Dugin doesn't have any real influence at the Kremlin."

Clarke agreed that if Ukraine were to assassinate a high-profile Russian, Dugina would not be its choice.

"I still suspect this was done by another entity, including the possibility that this was an inside job," he said.