MOSCOW—Russia sent paratroopers to help Kazakhstan’s leader stamp out a wave of protests as, further west, Russian President Vladimir Putin confronts the U.S. and its allies over the future of another former Soviet republic, Ukraine.

Dozens of people were killed in clashes between protesters and Kazakhstan’s security forces in the early hours of Thursday, including 18 law enforcement officers, according to Russian state media. Initially sparked by a sharp increase in fuel prices at the beginning of year, the protests quickly spiraled into a broader outpouring of frustration with the resource-rich nation’s authoritarian leaders. Protesters accuse them of squandering its wealth, including its uranium reserves, echoing the kind of uprisings that toppled one of Mr. Putin’s protégés in Ukraine in 2014 and a wave of protests against Belarus’s pro-Kremlin leader in 2020.