Volodymyr Zelensky was elected president of Ukraine in 2019, partly on a promise to root out systemic corruption.

But now critics say his government is trying to undermine some of Ukraine’s most important anti-corruption organizations as they pursue investigations into his administration.

One of Ukraine’s most prominent anti-corruption advocates and a frequent critic of the Zelensky administration, Vitalii Shabunin, was accused in a court proceeding last week of evading military service and fraud. He has denied the accusation, which his many domestic and international defenders say lacks merit. If convicted, he could face a decade in prison.

On Monday, even as the country came under yet another large-scale bombardment in its grueling war with Russia, Ukrainian security agencies directed dozens of raids on Ukraine’s National Anti-Corruption Bureau and the Special Anticorruption Prosecutor, saying that Russian intelligence had infiltrated the organizations.

And on Tuesday, the Ukrainian Parliament, which Mr. Zelensky’s party controls, passed a law that — if signed by the president — would give Ukraine’s prosecutor general, who was appointed by Mr. Zelensky, new powers over investigations by the two agencies.

Activists and analysts say these developments are part of a broader crackdown on independent media, government oversight agencies and other voices critical of Mr. Zelensky’s administration. And they warn that the efforts threaten to dismantle years of hard-won democratic reforms.