Two bridges inside Russia’s Belgorod region were destroyed by Ukrainian forces in a strike that not only showed the audacity of Ukraine’s long-range attacks on the Russian Federation, but also how cheap first-person-view (FPV) drones are finding more creative ways to use to great effect on the battlefield.

The targets, in the Belgorod region of Russia near the border with Ukraine’s Kharkiv region, were stashes of Russian mines and ammunition hidden under the bridges, and were destroyed by the 58th Separate Motorized Infantry Brigade. “It became clear that something was going on there,” a representative of the unit told CNN. Because they had been under the bridge, the unit’s standard reconnaissance drones could not get close enough to see, losing the signal before they got close enough. Instead, they sent an FPV-equipped drone with fiber optics to scout.

The drone spotted a large cache of anti-tank mines and ammunition hidden under the bridge. “We saw the mines, and we struck,” the brigade representative told CNN.

Footage released by the 58th Brigade shows the drone approaching the bridge before spotting the ammunition under the bridge and detonating in a massive explosion. A second camera that was set up nearby captured the blast from afar. CNN confirmed the bridge was located inside the Russian Belgorod region, just across the border from Ukraine’s Kharkiv region.

After the success of that strike, the unit then proceeded to another bridge in the area and found it was also mined. A second drone was sent to hit the other target, which also exploded in a large blast. “(We) saw an opportunity and took it,” the brigade said.

The drones that hit the bridges cost 25,000–30,000 Ukrainian hryvnias, or about $600–$725 each. Those figures put them at less than the price of a modern smartphone. While the drones were able to hit targets at ranges of up to 200 kilometers (124 miles), under normal circumstances, to hit bridges so deep inside Russia, Ukraine would need to use expensive guided missiles or precision bombs.

Ukraine has in the past used such missiles to target infrastructure in Russia, including from the US-supplied HIMARS rocket artillery systems. The HIMARS systems themselves cost millions of dollars each, while each rocket costs tens of thousands of dollars apiece. Each of the drones that hit the bridges in Belgorod was less expensive than a single HIMARS rocket.

The operation comes as Russia’s western command has been making slow gains in eastern Ukraine and at the same time continues to carry out near-daily missile and drone strikes against Ukrainian cities. Meanwhile, Russian President Vladimir Putin has snubbed any notion of a ceasefire with Ukraine, with a meeting of his so-called security council on Thursday suggesting that he wants to continue the offensive.

The attacks on the bridges in Belgorod therefore not only showed Ukraine’s willingness to hit targets inside the Russian Federation but also provided a welcome jolt to a front that has not seen many such moments in recent weeks.

Russia has not made any official comments on the attack. But it does mean that the loss of the two bridges will force it to find alternative routes to resupply its forces in the Belgorod region, especially those close to the Ukrainian border. One of the larger targets hit by Ukraine has been a supply depot of Russia’s 95th Guards Air Assault Division near the Ukrainian village of Izium.

For Ukraine’s military, the Belgorod attacks are a reminder that so far, at least, innovation is key to survival. With supplies often limited and Russia fielding more troops and vehicles, Ukraine has often had to improvise on the battlefield. Such FPV drones are part of that innovation, with many being cobbled together from commercial parts and modified by volunteers at home and abroad.

“The value of these drones cannot be overstated,” said a representative from the 58th Brigade. “They allow us to achieve results that would otherwise require weapons we don’t have.”