Vladimir Putin has accused the UK of making "ungrounded accusations" against Russia over the novichok poisonings in Wiltshire.
The Russian president said he did not even know the surnames of the Amesbury couple exposed to the nerve agent and the British government had failed to provide any evidence.
Dawn Sturgess, 44, died on 8 July, while her partner Charlie Rowley remains in a serious condition in hospital after coming into contact with novichok.
Police are investigating whether the pair were exposed to the same batch used in the attempted murder of former Russian spy Sergei Skripal and his daughter Yulia in nearby Salisbury in March.
After his controversial summit with US President Donald Trump in Helsinki, Mr Putin said Britain had not answered many questions surrounding the poisonings.
He told Fox News: "We would like to get at least some sort of document or evidence about it but nobody gives it to us.
"We recently heard that two more people have recently suffered from a nerve agent that is called novichok. But I've never even heard of the last names of these persons? Who are they?
"What kind of package? What kind of bottle? What is the chemical formula? Who got it?
"Maybe there are other reasons of death. Maybe it's the internal reasons within the United Kingdom but nobody wants to look into the issue.
"We just see the ungrounded accusations."
Home Secretary Sajid Javid has accused Russia of using Britain as a "dumping ground for poison" and called on Moscow to give a proper explanation for the Salisbury and Amesbury poisonings.
Mr Rowley's brother said the deadly nerve agent was in a perfume bottle found in the victim's house.
Ms Sturgess' teenage son Ewan Hope had urged Mr Trump to raise the issue with Mr Putin during their meeting in Helsinki but it was not addressed in their joint news conference.
More from Amesbury poisoning
2:04More than 400 exhibits, samples and items have been recovered by police investigating the poisoning of Mr Rowley and Ms Sturgess.
Russia has strongly denied involvement, sparking a row that has led to diplomatic expulsions between Britain and its allies and Russia.
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