There was no warning, no whistling sound of a missile or buzz of a drone that usually heralds a Russian attack. There was just an explosion, a resident said, and then a pile of smoldering rubble where a small shopping center once stood.

Local officials say the device used in that attack on the southeastern Ukrainian city of Zaporizhzhia last month was a Russian glide bomb — the first indication, they say, that Russia would begin targeting their city with the powerful weapon.

Since then, local officials say, glide bombs have frequently struck the city, wounding more than 100 people and killing at least two. They are considered especially dangerous because they are hard to intercept.

“They suddenly go boom,” said Stanislav, a retiree, describing the attacks. “We are worried.”

Glide bombs have been deployed by Russian forces to pound Ukrainian frontline positions throughout the war, and have been used against cities close to the Russian border, like Kharkiv, in recent months. But major cities farther from the border, like Zaporizhzhia, that were once seen as out of reach of the weapons are increasingly being struck, local officials, residents and military experts say.

It is unclear why Zaporizhzhia — once considered relatively safe — has come under attack by the glide bombs, which are unguided Soviet-era bombs converted into long-range, precision weapons with a “guidance kit” of small wings and fins. The bombs are launched from planes, usually at a safe distance from Ukrainian air defenses, and then glide to their targets.

Many experts say they believe that Russia is now able to hit Zaporizhzhia because it somehow modified the bombs to extend their range.