A senior Russian occupation official on Thursday said that Defense Minister Sergei K. Shoigu should consider killing himself because of his army’s failures in Ukraine, a remarkable challenge to the authority of President Vladimir V. Putin, who, after cracking down on Russia’s liberal opposition, now faces growing dissent in his own camp.

“Many people are saying that as an officer, the defense minister could simply shoot himself for being the one who let things get to this state,” Kirill Stremousov, the Russian-imposed deputy governor of the Kherson region of southern Ukraine, said in a video posted to his account on the Telegram social network. “But, you know, the word ‘officer’ is not understood by many.”

The outburst was the latest in an extraordinary barrage of criticism from pro-Kremlin officials and state media figures directed at the leadership of the Russian military. Last month, it was largely pro-Russian bloggers who were voicing anger over the failings of military planning that led to the Russian army’s being routed in northeastern Ukraine. But after Russian forces were forced to retreat in two other sections of the front line in the last week, prominent officials have increasingly joined the chorus.

“They need to stop lying,” Andrei Kartapolov, the head of the defense committee in Russia’s lower house of Parliament, said on Wednesday, excoriating the Defense Ministry for covering up the bad news from the front. “Our people aren’t stupid, far from it, and they see that they are not being taken seriously. It’s not being considered necessary to tell them even part of the truth, let alone all of it.”

Mr. Shoigu, who is seen as one of Mr. Putin’s closest associates and has vacationed with him in Siberia, has not responded to the criticism, and Mr. Putin has not commented on it. There were indications that the criticism was part of infighting in the Russian ruling elite that was spilling into the open, coming on the heels of a tirade against the military leadership that Ramzan Kadyrov, the strongman ruler of the southern Russian republic of Chechnya, published over the weekend.

The common thread in the criticism has been that Russia’s military, despite the country’s enormous defense budget, has turned out to be unprepared for a real war. Many Russian hawks have been calling on the military for months to escalate its offensive. And while they celebrated Mr. Putin’s draft as a way of turning the tide in the war, they have criticized the military for its poor execution of it.

“So what’s the genius idea of the General Staff?” Vladimir Solovyov, a prominent state television host, said on his online talk show on Thursday. “Just explain it to me, dear people who have received all the necessary budget resources for so many years.”

Some of the most blunt criticism was laid out in a widely shared Telegram post by Oleg Tsaryov, a former separatist official in eastern Ukraine, who said that while Russian military leaders need not commit suicide, they should resign, “like European officials do in cases of public failures.”

Mr. Putin would not have invaded Ukraine, he wrote, “if the Defense Ministry had not guaranteed that the goals and tasks of the special operation could be accomplished in the time frame that was set.”

“With their actions or their inaction, the ministry’s leadership has ended up putting Russia’s existence under threat, and brought the world to the brink of nuclear war,” he wrote.