A principal voice of opposition against President Vladimir Putin says he has a 50-50 chance of being killed at the order of his rival.

"Well, like, 50 percent I would be killed, or I would not be killed," said Alexei Navalny said in a recent interview with CBS News, which will be aired in full on Monday.

Navalny was jailed for embezzlement for three and a half years in 2014. His sentence was suspended after protests, but his brother who was convicted with him remains in prison.

He told CBS News that his brother Oleg was sentenced for the same period of time, but remains in jail, he believes, "because he's my brother. It's the only reason."

Navalny has since been a victim of chemical attacks, which he believes was ordered by the Putin regime.

"This attacker ... was coordinated, and hired by government and administration of Putin. And we have a lot of evidence to that," said Navalny.

"Mr. Putin personal[ly] decides such things, and no one understands what is in his head," he said in response to questions about his being jailed again by the regime.