Moscow has accused Ukraine of poisoning a number of Russian servicemen in the Russia-controlled part of the ex-Soviet republic's southeastern region of Zaporizhzhia in late July.
The Russian Defense Ministry announced the information on Saturday, saying the servicemen in that region had been taken to a military hospital with signs of serious poisoning on July 31. Tests showed a toxic substance, namely botulinum toxin type B, in their bodies, the ministry added.
Botulinum toxin type B is a neurotoxin that can cause botulism when ingested in contaminated food products.
The ministry said the poisoning amounted to “chemical terrorism,” adding, “Russia is preparing supporting evidence with the results of all the analyses."
Ukraine's Defense Ministry did not immediately respond to a Reuters request for comment, but Interior Ministry adviser Anton Gerashchenko commented on the Russian accusations.
"The department (Russian Defense Ministry) does not clarify whether the poisoning could have been caused by expired canned meat, in which botulinum toxin is often found," he said.
Back in March, the Russian Defense Ministry said it had found evidence of United States-funded biolabs in Ukraine, which had urgently destroyed samples of deadly pathogens when Russia began a “special military operation” in the neighboring country a month earlier.
The ministry said it had been closely monitoring the bioweapons programs that were developed by the Pentagon in post-Soviet countries, adding that according to new findings, a “network” of more than 30 biological laboratories had been formed in Ukraine in particular.
Documentation was received from Ukrainian biological research laboratories on the urgent destruction of dangerous pathogens on February 24, including anthrax, cholera, and the plague, in what could be a cover-up of Biological and Toxin Weapons Convention (BTWC) violations.
According to Russian President Vladimir Putin, the Russian operation in Ukraine, which was launched on February 24, is aimed at “demilitarization” of the Donetsk and Lugansk Republics in eastern Ukraine, which are collectively known as the Donbas region.
The two republics broke away from Ukraine in 2014 after refusing to recognize a Western-backed Ukrainian government that had overthrown a democratically-elected Russia-friendly administration.
Announcing the operation, Putin said the mission was aimed at “defending people who for eight years are suffering persecution and genocide by the Kiev regime.”
Drone shot down over Russia's Black Sea fleet headquarters
Separately, it was reported on Saturday that a drone had been shot down over the headquarters of Russia's Black Sea fleet in Crimea, a local official said.
"The drone was shot down just above the fleet headquarters" in the city of Sevastopol, city governor Mikhail Razvojaev wrote on Telegram, blaming the attempt on Ukrainian forces.
"It fell on the roof and caught fire," he said, adding that there was no major damage or victims.
It was the second assault of its kind against the fleet’s headquarters in less than a month.
On July 31, Moscow said a drone attack by the Ukrainian military had wounded six people at the site, prompting Russian officials to cancel planned festivities there.
Crimea voted to break away from Ukraine and join Russia in 2014.
"Russia strikes on south Ukraine injures 12"
In another development also on Saturday, Ukraine prosecutor’s office said twelve Ukrainians were wounded after Russian forces attacked an apartment block and several houses in the city of Voznesensk, near a key nuclear plant.
"According to preliminary information, 12 people including three children were injured. Two children are in a serious condition," the prosecutor's office said on Telegram.
Voznesensk is located about 20 kilometers (12 miles) from the nuclear plant at Pivdennoukrainsk, which is Ukraine's second largest, and 70 kilometers from Mykolaiv, the regional capital.
The strikes hit an apartment building and several homes in the city, which is home to 30,000 people, the emergency services said on Facebook.
Meanwhile, the Ukrainian army said they had downed four Kalibr high-precision sea-launched cruise missiles fired from the Black Sea near the central city of Dnipro.