It comes as discussions between Ukrainian and Russian delegations are set to continue in Turkey on Tuesday.
Following fears of being poisoned, Ukraine has issued a warning to its negotiators.
Ukraine warned those negotiating with Russia not to eat or drink with them.
Ukrainian Foreign Minister, Dmytro Kuleba gave the warning following a report about the poisoning of Russian billionaire Roman Abramovich and Ukrainian negotiators.
“I advise anyone going through negotiations with the Russian Federation not to eat or drink anything.
“Preferably avoid touching any surface,” Kuleba said.
It comes as discussions between Ukrainian and Russian delegations are set to continue in Turkey on Tuesday.
In more than a month of war, negotiators from Ukraine and Russia have met three times in the border region of Belarus, talks then shifted online.
On Sunday, the Turkish presidential office named Istanbul the venue for the next talks.
According to him, a face-to-face meeting would allow for more substantive negotiations than a video link.