The Russian authorities said on Sunday that a car bomb killed the adult daughter of a prominent Russian ultranationalist whose writings are believed to have influenced President Vladimir V. Putin’s invasion of Ukraine.
The authorities said they had opened a murder investigation into the death of the woman, Daria Dugina, after a Toyota Land Cruiser exploded on a highway 20 miles west of Moscow and burst into flames, scattering pieces across the road. State news media identified her as the daughter of Aleksandr Dugin, an outspoken supporter of Russia’s war in Ukraine, whose car she was driving.
There was no immediate claim of responsibility for the incident. Russian news media said that associates of Mr. Dugin believed that he, not his daughter, was the target.
A Ukrainian official disavowed his country’s involvement. But pro-Kremlin commentators and politicians quickly blamed Ukraine and demanded revenge, injecting new uncertainty into a war that has lasted nearly six months.
Russian investigators said that an explosive device had been planted underneath the car on the driver’s side and that the attack was believed to have been “a premeditated crime.”
Mr. Dugin is a self-educated political philosopher known for pushing a vision of a more powerful, aggressive Russia. He is frequently described as “Putin’s brain,” although the actual relationship between the two men is opaque.
The United States has imposed sanctions against Mr. Dugin for supporting militants in eastern Ukraine. Ms. Dugina, 29, shared her father’s views and promoted them as a radio and TV anchor. In July, the British government imposed sanctions on Ms. Dugina, citing her as a “frequent and high-profile contributor of disinformation in relation to Ukraine and the Russian invasion of Ukraine on various online platforms.”
Russia’s Investigative Committee — the country’s version of the F.B.I. — said in a statement that Ms. Dugina had died at the scene of the blast in the Odintsovo district, an affluent area of Moscow’s suburbs. “The identity of the deceased has been established: it is the journalist and political scientist Daria Dugina,” the statement said.
Images and videos circulating on Russian social media showed a vehicle engulfed in flames and car parts blasted across the road. A man who appeared to be Mr. Dugin paced back and forth, holding his hands to his head, as fire trucks rushed to put out flames. These images could not be immediately verified.
Zakhar Prilepin, a popular conservative writer, said in a post on his Telegram channel that Mr. Dugin and his daughter were at a nationalist festival on Saturday but left in different cars. The festival, called Traditions, gathered prominent Russian nationalist figures. Mr. Dugin gave a lecture on the “metaphysical dualism of historical thinking,” according to the festival’s website.
Russian state media described the festival as a relatively low-security event. The state-run news agency Tass cited an unnamed law-enforcement source as saying that there were no security checks at the entrance to the parking lot where the car driven by Ms. Dugina had been parked.
The incident came as the Kremlin faces intensifying questions over its war effort in Ukraine and why it is not doing more to prevent attacks deep behind the front lines. Prominent supporters of the war — already angry over recent Ukrainian sabotage attacks in Crimea — quickly took to social media with claims that Ukraine was behind Ms. Dugina’s death.
A senior Ukrainian official denied responsibility for the attack.
“Ukraine certainly had nothing to do with yesterday’s explosion,” Mykhailo Podolyak, an adviser to Ukraine’s president, said in televised comments on Sunday morning. “We are not a criminal state like the Russian Federation, much less a terrorist one.”
Denis Pushilin, the head of Russian-backed separatists in the Donetsk region of eastern Ukraine, wrote on the Telegram social network that the “terrorists of the Ukrainian regime” were behind the car bombing.
The Russian Foreign Ministry’s spokeswoman, Maria V. Zakharova, stopped short of accusing Ukraine. But she wrote on Telegram that if Ukraine was indeed responsible, “then we have to be talking about a policy of state terrorism being realized by the Kyiv regime.”
“We are waiting for the results of the investigation,” she wrote.