Russian President Vladimir Putin might remain in office for the rest of his life, he acknowledged Friday.

"I have not yet decided yet whether I will leave the post of the president or not," Putin told students during a question-and-answer session in Sochi. "Only after I answer this question for myself will I think about my next step."

Putin has led the Russian government since 1999, when he rose to power under outgoing President Boris Yeltsin. He served two terms as president before constitutional term limits required him to leave office. He spent the next four years as prime minister and then returned to the presidency in the next election.

"There are a lot of interesting things to do in the world," Putin continued, in reply to a student who asked about his post-presidency plans. "There are public organizations and there are other areas that are very interesting to me, for example, ecology... First, the main question should be answered."

When Putin returned to the presidency in 2012, opposition leaders accused him of rigging the election, a charge also levied against his political party in the 2011 parliamentary campaign. Then-Secretary of State Hillary Clinton echoed those criticisms, thereby supplying Putin with a motive for the 2016 cyberattacks against the Democratic Party, according to U.S. intelligence officials.

"Putin most likely wanted to discredit Secretary Clinton because he has publicly blamed her since 2011 for inciting mass protests against his regime in late 2011 and early 2012, and because he holds a grudge for comments he almost certainly saw as disparaging him," the Office of the Director of National Intelligence said in a January report.

Putin's domestic opponents believe that his career plans also played into the decision to annex Crimea and invade eastern Ukraine in 2014, starting a conflict that has continued despite ceasefire agreements and international sanctions on Russia. "The annexation of Crimea to Russia with the active support of state propaganda enabled Putin to strengthen radically his own legitimacy," opposition leader Boris Nemtsov wrote in an anti-Putin report. "His popularity rating reached record levels."

Nemtsov was murdered while working on the report, which was published after his death. A group of Chechen men were convicted of the killing, but Russian officials haven't identified the person who paid for the assassination.

"The president has repeatedly said that such cases are very hard to investigate, but this does not mean that someone could one time give up the search for the criminals. Sometimes such processes take years," Putin spokesman Dmitry Peskov said in June. "Of course, the inevitability of punishment must be observed, but objectively we must agree that these cases are extremely hard."