The wife of Ukraine’s military intelligence chief has been poisoned and is recovering in a hospital, Ukrainian intelligence officials said on Tuesday, an incident that has led to widespread speculation that Russia was stepping up efforts to target Ukraine’s senior leadership.
Andriy Chernyak, an official from the Ukrainian military intelligence agency, said that Marianna Budanova had been poisoned and was receiving treatment. Her husband, Kyrylo Budanov, is the head of the agency known as GUR and is one of the country’s most senior military leaders.
Mr. Chernyak declined to speculate on the perpetrator or the type of poison used and provided no further details, citing the ongoing investigation.
The agency’s spokesman, Andriy Yusov, later issued a statement with a similar account of the incident and said more information would be released as the investigation proceeds.
The suspected poisoning of Ms. Budanova was first reported by the Ukrainian news outlet Babel. It said that doctors found a large amount of heavy metals in Ms. Budanova’s system that are “not used in any way in everyday life and military affairs.”
Mr. Budanov had not fallen ill, the Ukrainian officials said.
The reports that Ms. Budanova had been poisoned sparked immediate suspicion in Ukraine that Russia, which has a long history of using poison as a tool to exact revenge and eliminate perceived enemies, may have been responsible.
Mr. Budanov has often stated that Russia planned to kill him and Mr. Yusov, the spokesman for the intelligence agency, said this summer that there had been at least 10 attempts by Russia to do so.
The circumstances of the poisoning and how Ms. Budanova had been affected were not immediately clear. But Mr. Budanov told Radio Liberty earlier this year that since Russia launched its full-scale invasion in 2022, his wife, a psychologist who worked as an anti-corruption adviser to the mayor of Kyiv, Vitali Klitschko, had essentially moved into her husband’s office.
If Russia was able to poison Ms. Budanov, it would suggest that its agents were operating closer to the inner circles of power in Kyiv than previously thought possible.
Viktor Yahun, the former deputy head of the domestic intelligence agency, the Security Service of Ukraine, has participated in past investigations into poisonings and said more information was needed before it would be possible to assess the Budanova case.
But Mr. Yahun said he would be surprised if Russia had agents in Ukraine who could get close to Ms. Budanova or her husband.
“It just doesn’t have the needed kind of agents on the territory of Ukraine that would be able to poison someone,” he said.
However, Oleksiy Danilov, the head of the National Security and Defense Council of Ukraine, said in an interview before the poisoning was announced that Russia was activating sleeper agents and ramping up its efforts to destabilize the government in Kyiv.
“In 2003, Putin set himself the task of destroying our country, and during all this time their tasks have not changed,” he said. “Considering the fact that the Russian Federation does not have the ability to win by military means, it is now using all its agent networks, which, unfortunately, still exist. And now we are observing their maximum activation.”
Mr. Budanov has an outsize public profile for the leader of a clandestine agency and is often portrayed in the media as the mastermind of some of the boldest attacks on Russian targets behind enemy lines.
Fond of wearing a pistol on his hip when meeting with journalists, Mr. Budanov has said that Ukraine has the right to assassinate Russian war criminals anywhere in the world they might try to hide. He is proud of comparisons made between his agency and the Israeli Mossad.
“They have been trying to accuse me of terrorism since 2016,” he said in one interview. “What they call ‘terrorism’ we call liberation.”
Russia has targeted senior Ukrainian leaders in the past, including President Volodymyr Zelensky, according to Ukrainian officials.
Mr. Zelensky has said he is not longer shaken when he learns of new plots on his life.
“The first one is very interesting,” he said in a recent interview with The Sun, the British tabloid, “and after that it is just like Covid.”
In 2004, Viktor A. Yushchenko, the Ukrainian opposition candidate at the time, fell ill and developed a broad array of painful and disfiguring conditions that plagued him during the final three months of the presidential campaign.
His opponents ridiculed his claims that he had been poisoned, saying that the once-telegenic candidate had been stricken by bad sushi or too much drink. But doctors in Vienna later established that he had been poisoned with dioxin, a highly toxic waste product of various industrial chemical processes.
After it was revealed that Mr. Yushchenko had been poisoned, Alexander V. Litvinenko, who served in the K.G.B. and its Russian successor, the Federal Security Service, from 1988 to 1999, told The New York Times that Russian intelligence believes “poison is just a weapon, like a pistol.”
Less than two years later, Mr. Litvinenko died after being poisoned by a rare radioactive isotope. An exhaustive 328-page report by a retired British High Court judge found there was “strong circumstantial evidence of Russian state responsibility” and that the Russian president, Vladimir V. Putin, and the head of the F.S.B. likely sanctioned the murder.
In 2018, Sergei V. Skripal, a former Russian spy, was found twitching beside his unconscious daughter on a park bench in Salisbury, England, both poisoned, British authorities later said, with a potent nerve agent administered by two officers from Russia’s military intelligence agency.
And in 2020, Aleksei A. Navalny, a Russian opposition leader now in jail, accused the Kremlin of trying to assassinate him by planting a deadly chemical on his underpants.
An investigation by Freedom House found at least 23 documented cases of transnational assaults since 2014, including poisoning attempts, most likely orchestrated by Russia.
After nearly every case, Russia mounted a vigorous disinformation campaign aimed at distancing the government from the killings.
Poison has long been a preferred tool of assassins because it can be tasteless, odorless and hard to detect. It can cause symptoms that mimic natural illnesses, causing confusion and complicating investigations.
But poisons do not always work and can be affected by variables including the dosage, delivery method and the target’s health.
Anna Politkovskaya, a Russian journalist known for scathing criticism of Kremlin policies, suspected she was poisoned after she lost consciousness after drinking tea on a flight in Russia.
She survived but was shot to death in a contract killing in her Moscow apartment block in 2006. The man convicted of her murder was recently pardoned by Mr. Putin for his military service in Ukraine.