Some of Germany’s allies are urging Berlin to tighten security around classified information after Russia revealed sensitive discussions about aid for Ukraine, people familiar with the discussions have said.

Officials from NATO countries expressed concern about seemingly careless operational security that resulted in the leak of a conversation between German military officers, including the use of commercial, nonencrypted platform WebEx for the meeting.

One called the lackadaisical measures unprofessional, and said that such behavior would be expected from people who have never had security briefings but not from military officials. Another said they were not surprised by the lapse from Germany, while a third said the leak would likely result in tighter measures across the board, but particularly in Germany. All asked not to be named due to the sensitivity of the matter.

Germany has started an investigation into the incident and on Monday urged allies not to allow Russia to sow division among them.

Last week, Russian media published what it said was a private discussion between high-ranking German air force officials about supplying long-range Taurus missiles to Ukraine — something Chancellor Olaf Scholz has repeatedly ruled out. As well as questioning the chancellor’s stance, the officers also disclosed details of British and French troops operating on the ground in Ukraine and discussed targeting the Kerch Strait Bridge, which connects the occupied Crimean peninsula with the Russian mainland.

The incident has revived the rift between Germany and its allies over supplying high-grade weapons, irritated the French and the British and handed a propaganda opening to the Russians.

Putin’s spokesman, Dmitry Peskov, said Monday the recording showed that Germany’s armed forces are discussing plans to strike Russian territory. The leak "confirms yet again that the countries of the so-called collective West are directly involved in the conflict,” he told reporters on a conference call, according to Tass.

"We’re all working together to try to support Ukraine and the Germans have been right there, absolutely,” White House spokesman John Kirby said Monday. "We look forward to continuing to work with Chancellor Scholz and his government as they continue to find ways to support Ukraine.”

According to the transcript, the officers discussed the presence of western trainers on the ground in Ukraine to help forces operate weapons systems as well as detailed information about how some of the allies sent some of their most modern equipment.

A German official speaking on condition of anonymity said that the incident showed that the shift in security and defense policies prompted by the war in Ukraine remains a work-in-progress and that in future many more meetings would be held in person to limit the security risks.

"It’s obviously very, very concerning,” said Arndt Freytag von Loringhoven, a former German ambassador and NATO intelligence chief, in a telephone interview, recalling that a former intelligence official was recently charged with spying for Russia. "We have two issues almost at the same time. Both add up to increase skepticism in our security culture and in Germany,” he added.

In late 2022, Germany took that official into custody after he allegedly passed on classified information to a Russian intelligence service. German officials are worried he may have passed on information that was shared by the U.S. National Security Agency and U.K. intelligence agencies, Focus magazine reported at the time.

While the latest incident is another embarrassment for Germany, the allied officials played down the importance of the information that was published, pointing to Germany’s known and public opposition to sending the Taurus missiles. They also stressed the importance of staying united despite the incident.

The U.S. has also been grappling with its biggest intelligence leak in a decade. Last April, the FBI arrested Jack Teixeira, a 21-year-old Air National Guardsman, in connection with the leak of highly classified documents including maps, intelligence updates and the assessment of Russia’s war in Ukraine.