The agency cited Ukraine's Prosecutor General Oleksandr Medvedko as saying that this was a response by the Russian Prosecutor General's Office to a request by Ukraine as part of a probe into the poisoning of Viktor Yushchenko during his 2004 election campaign.
"In the answer we have received, the Russian side claims dioxin of the quality specified in our letter is not produced there," Medvedko told a news conference.
He added referring to the letter that dioxin of that kind had been produced in Russia some time earlier but had never been exported.
Medvedko said his office had sent another letter to Russia with a request for details.
Yushchenko fell ill shortly after a dinner September 5, 2004 with the then security service head Ihor Smeshko, and his deputy, Volodymyr Satsiuk, whom he invited to discuss the election campaign.
On September 6, Ukrainian doctors diagnosed food poisoning, and on September 10, as he failed to improve, Yushchenko was taken to the Rudolfinerhaus clinic in Vienna, which he left later in the month for the election campaign.
Medical experts involved, including from the U.S., Austria and Great Britain, were divided over the cause of the illness, but in late 2004 the Rudolfinerhaus clinic finally confirmed that he had indeed been poisoned with dioxin.
In September 2007, Yushchenko said in an interview with Britain's The Times that Russia thwarted the probe into his poisoning by refusing to offer samples of dioxin produced in the country.
On September 13, Russia agreed to assist the probe and invited Ukrainian experts.
