Roughly comparable to the more advanced American JDAM guided bombs, these glide bombs are large Soviet-era munitions retrofitted with guidance systems that experts say often fail — resulting in impacts on Russian territory.

The majority of the bombs were discovered by civilians — forest rangers, farmers or residents of villages surrounding the city. In most cases, the Defense Ministry didn’t know when the bombs had been launched, indicating that some of them could have been there for days.

According to the document, at least four bombs fell on the city of Belgorod itself, a regional hub with a population of about 400,000 people. An additional seven were found in the surrounding suburbs. The most, 11, fell in the Graivoron border region where some could not be recovered because of the “difficult operational situation.”

The document, originally intercepted by Ukrainian intelligence and passed on to The Post, includes a spreadsheet of incidents citing emergency decrees on bomb cleanup and evacuation and appears to be a product of the Belgorod city emergency department.

Astra, an independent Russian media outlet, verified that many of the incidents in the document matched those it had collected from local governments and reports in local news media. People mentioned as witnesses have been confirmed as residents.

While the bombs usually fail to detonate, one of the first recorded hitting Belgorod in April 2023 did explode when it crashed into a normally busy street, creating a crater 65 feet wide, shattering windows, and hurling parked cars onto roofs of buildings. The impact happened at night, however, and no casualties were reported. A day later a second, unexploded bomb was found buried 23 feet into the ground.

Russian military acknowledged at the time that the “accidental release of aircraft munition” from a Russian Su-34 fighter-bomber was behind the explosion. The document later confirmed it was FAB-500, a glide bomb, carrying a 500 kilogram, or 1,100 pound, payload.

Local authorities generally remain quiet about the incidents, only reporting “accidents,” blaming Ukrainian shelling or just not reporting the various explosions rattling the area, particularly more recently.

On May 4 — after the period covered by the document — another bomb fell on Belgorod, injuring seven people and damaging more than 30 houses in a small community. Citing a source in the emergency services, the Astra media outlet reported it was also a FAB-500.

Gov. Vyacheslav Gladkov said only that “an explosion happened.”

“The governor always reports what exactly caused the explosion, but this time he decided not to disclose it,” independent local outlet Pepel noted at the time. “This indirectly confirms that the explosion was caused by a Russian air bomb that fell on the house during the bombing. The nature of the destruction also indicates this.”

On May 12, another blast destroyed several stories of an apartment block in Belgorod, killing 17 people. The Russian military blamed a Ukrainian missile, while the Conflict Intelligence Team, a Russian research group specializing in open-source investigations, said video from the scene indicated it was the result of another accidental FAB-500 bombing or a rogue antiaircraft missile fired by a Russian defense system.

On June 15, an explosion took place in the town of Shebekino, near Belgorod, and part of a five-story building collapsed, killing at least five, likely another glide bomb mishap.

According to its own tallies, Astra estimated that Russia has accidentally dropped more than a hundred bombs on its own territory as well as occupied areas in eastern Ukraine over the past four months — the same period that has seen a major increase in the use of glide bombs.

The Russian government has not responded to a request for comment on the document or reports of failed glide bombs.

The glide bombs are a Soviet relic hailing from the Cold War, designed as “dumb bombs” to be dropped on a target. Russia adapted this large inventory of unguided bombs to modern warfare by retrofitting them with guidance systems known as UMPK kits — cheap pop-out wings and navigation systems.

This allows Russian Su-34 and Su-35 jets to launch them from a distance of about 40 miles, which is out of reach for most Ukrainian air defense systems.

“A certain percentage of Russian bombs is defective. This problem has existed since they started using these UMPK kits and it’s not being fundamentally solved. We think these accidental releases are caused by the unreliability of these kits, something that does not seem to bother the Air Force,” Ruslan Leviev, a military expert with the Conflict Intelligence Group that has been tracking Russian military activities in Ukraine since 2014, said in a recent front line update.

“According to our estimates, only a fraction of these bombs fail, so it doesn’t affect the practical effectiveness of this weapon, no matter how cynical that may sound,” Leviev said. “Unlike Western high-precision bombs, the UMPK kits are produced relatively cheaply and in large quantities, using civilian electronics, where reliability requirements are much lower.”

Based on statements from the Ukrainians about the numbers of bombs launched and the tallies from Astra about misfires, the CIT estimated a failure rate of 4 to 6 percent.

“Under normal conditions, such a system would need to be improved, at a minimum, to avoid falls on populated areas on our territory, which we have already seen and which also led to casualties,” the group said to The Post in response to queries on the misfires. “We don’t know whether the Russian Federation is currently spending resources on this. Perhaps they are quite happy with this situation.”

The fact that most of the bombs whose guidance systems fail and fall on Russian territory don’t detonate suggests there is some kind of failsafe system to keep them from exploding in such cases, the CIT added.

Glide bombs are also not as precise as cruise missiles, and often miss the target, but because of sheer explosive power they still do significant damage.

The glide bombs have put added pressure on Ukraine’s ground-based air defenses and have been instrumental in Russia’s demolition of Avdiivka, which its troops conquered in mid-February, marking its most significant gain since the capture of Bakhmut a year ago.

“Those weapons allow Russia to supplement an inadequate inventory of tactical air-launched missiles and to avoid using free-fall bombs that expose pilots to a greater risk of being shot down,” according to recent analysis by the International Institute for Strategic Studies.

Ukraine’s best defense against them is the U.S. Patriot surface-to-air missile that can destroy a Russian aircraft before it approaches to release the bomb, but the systems are in short supply.

In late March, the Defense Ministry announced the development of a new, heavier version of the glide bomb, the FAB-3000, weighing twice as much as the next-biggest model. The number corresponds to the weight in kilograms, making it more than 6,000 pounds. It was finally deployed June 21 against the Ukrainian village of Liptsy.

The ministry also said the production of the lighter FAB-500 and FAB-1500 had been drastically increased.

The misfires for the enormous new FAB-3000s are already being reported. On June 29 one crashed into an empty field near Shebekino and exploded, but there were no casualties, according to Astra.