Russia accused Ukraine on Sunday of striking one of its nuclear power plants in an overnight drone attack that caused no increase in radiation levels. The alleged attack sparked a fire at the Kursk Nuclear Power Plant near the Russia-Ukraine border,

Russia has accused Ukraine of launching drone attacks that sparked a fire at a nuclear power plant in its western Kursk region overnight on Sunday, the same day the two countries said they've agreed to a prisoner swap.

Many of the drones aren’t particularly fast or high-tech, but they are cheap enough for the Kremlin to launch more than 700 in one night, in an effort to overwhelm Ukraine’s air defenses. Here’s what we know.