KIEV, May 17 (AP) - 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 May 11 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.