KYIV, Ukraine — Ukrainian anti-corruption activists are calling for a criminal investigation into Ukraine’s top defense institutions for alleged state treason, over allegations that tens of thousands of Ukrainian-produced mortar rounds critical to the country’s defense against Russian troops are failing to fire or badly misfiring.

The accusations of corruption that have dogged Ukraine’s defense sector are also a potential roadblock for future aid — and future investment into the country’s burgeoning defense industry — from Kyiv’s international allies.

The Anti-Corruption Action Center, one of Ukraine’s leading independent anti-corruption watchdogs, on Monday filed a petition to Ukraine’s domestic security service, the SBU, calling for an investigation of officials at the country’s Defense and Strategic Industries ministries as well as Ukroboronprom, the state defense industry conglomerate.

Officials in these government bodies “committed a series of acts” that prevented the mortar rounds from being used for their intended purpose, so as to “damage Ukraine’s defense capability,” the center said in its petition.

“From the facts already exposed it is beyond reasonable doubt that officials in charge for quality control were aware of the malfunction of the mortar rounds but intentionally allowed them to be sent to the Ukrainian armed forces,” said Daria Kaleniuk, the center’s executive director, in an interview.

Vitaliy Shabunin, head of the center’s board, posted the petition on Facebook on Monday. He also posted another one to Ukraine’s National Anti-Corruption Bureau, an independent government agency tasked with battling graft, for the alleged overpayment of some $90 million to a Polish firm for weapons.

The cases were “the two bloodiest corruption schemes in 2024,” Shabunin wrote.

Last month, Ukrainian media outlets reported that a significant portion of 120-mm caliber mortar rounds and a smaller number of 82-mm shells that had recently arrived at the front line were defective. The two mortar rounds are a key element of Ukraine’s defense against Russian infantry assaults.

Soldiers in one unit said that only one out of every 10 120-mm rounds managed to explode successfully, according to local media.

The allegations come at a sensitive time for President Volodymyr Zelensky’s government. Ukrainian forces are struggling with shortages of equipment and manpower while trying to hold back Russian advances along numerous points on the front line in Ukraine and Russia’s western Kursk region — and Zelensky, after years of vowing to fight for every inch of Ukrainian territory, has recently signaled a greater openness to entering into negotiations to end the war.

The accusations of corruption in its defense sector are also a key talking point among Republican politicians in the United States who oppose providing further military support to Ukraine, though the allegations do not apply to Western-donated weaponry.

Olena Tregub, a member of a group at Ukraine’s Defense Ministry that monitors defense sector procurements, emphasized that this was only one instance in the country’s burgeoning, multibillion-dollar domestic defense industry.

“I don’t want to play into the narrative that we are a corrupt, failed state because it’s not true,” she said. Still, the situation with the mortar rounds was “horrible and dangerous,” Tregub said.

“We are concerned because, we need those [rounds] on the front lines,” said Tregub, who also heads an independent commission that tracks corruption in the defense sphere, adding that it is “a critical situation if they’re not reaching their targets.”

The Defense Ministry last month issued a statement acknowledging the “malfunction of 120-mm mortar rounds,” which it said it was actively investigating.

Preliminary results suggested that the defects were caused by “low-quality powder charges or violations of ammunition storage conditions,” the ministry said, adding that “appropriate personnel decisions” would be made for officials found responsible.

The ministry said it had suspended the use of the affected batches of ammunition and that imported rounds would be used instead. The State Bureau of Investigation had also opened a criminal case, the ministry said.

However, the ministry did not provide details of how many mortar rounds were defective, or which officials were being investigated. The name of the company that produced the rounds has not been released for national security reasons, defense officials say.

Out of one shipment of 54,000 120-mm caliber rounds, almost half needed to be replaced, Strategic Industries Minister Herman Smetanin told Ukraine’s parliament in November. It was not clear what percentage this was of the total number of rounds that were defective, however.

Ukrainian media outlets reported the total number of faulty 120-mm mortar rounds to be closer to 100,000. While this figure could not be independently confirmed, a Ukrainian defense official, speaking on the condition of anonymity because of the sensitivity of the issue, said: “The original contract was for hundreds of thousands of mortar rounds, and now there is need to import about 20 percent of this quantity.”

The official also said that while the investigation into the production of the faulty rounds is underway, the company that produced them has not been blacklisted and is now sending proposals to produce “millions of shells of different calibers.”

The question at the center of the anti-corruption agency’s petition is whether Ukraine’s quality control bodies were aware, or should have been aware, of the shells’ defects.

The mortar rounds’ flaws were “obvious for anybody, who had ever worked with such kind of munition,” said Kaleniuk, the watchdog’s executive director, who also is involved in lobbying Ukraine’s allies for needed weapon systems. “And those on the production lines, as well as in authorized government bodies, obviously knew about it.”

The center was not accusing the entire Defense Ministry or Ministry of Strategic Industries, which oversees Ukraine’s domestic military production, Kaleniuk said — but rather “officials inside these agencies, who were engaged in decision-making” regarding the contract to produce mortar rounds.

Oleksandr Zavitnevych, the head of parliament’s national security, defense and intelligence committee, and a member of Zelensky’s political party, said that the defective rounds would be replaced at the expense of the manufacturer and that “quality control has been intensified across all production facilities.”

Those involved in Ukraine’s domestic arms industry are also concerned about what effect the allegations over shoddy quality control could have on Western investment into Ukraine’s defense industry.

As Ukrainian officials brace for what could be severe cutbacks in Western military aid next year, Kyiv’s international partners are funneling hundreds of millions of dollars to Ukrainian arms producers — including $800 million from the United States to help Ukraine produce long-range drones. Kyiv also hopes to become a major arms exporter in the years to come.

“Even one single mis-procurement can destroy the trust” of Western partners, said Maryna Bezrukova, the head of the Defense Ministry agency responsible for weapons procurement. “We should fix the mistake and show that this situation will not repeat in the future.”

“Sometimes production mistakes and technological mistakes happen in the U.S. and in Europe,” she said. “It also happens in Ukraine because we are under pressure and we are a country at war.”

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