The Security Service is investigating allegations of an assassination plot targeting top officials in Ukraine, including President Viktor Yushchenko, a spokeswoman said Thursday.
The investigation was launched after an official in Yushchenko's administration, Valery Heletey, claimed on Friday that he had information indicating that criminals and unnamed political parties were plotting to kill Yushchenko and his chief of staff, as well as political party leader Yulia Tymoshenko.
Security Service spokeswoman Maryna Ostapenko said the agency was looking into the allegations.
Yushchenko is locked in a power struggle with Prime Minister Viktor Yanukovych and is seeking to dissolve parliament, where Yanukovych has majority support, and hold new elections.
The acting chief of the Security Service is a Yushchenko appointee.
During the 2004 presidential election campaign, Yushchenko fell severely ill and was diagnosed as having suffered massive dioxin poisoning.
Russian officials have repeatedly declared that Israeli aviation poses a threat to the Russian military in Syria.