Israel says Iran has been firing cluster munitions throughout their 10-day war — adding a complicated and deadly challenge to Israel’s already-stretched air defenses.

The warheads burst open at high altitudes, scattering dozens of smaller bomblets across a wide area. The smaller bombs, which at night can resemble orange fireballs, are difficult to intercept and have proven lethal.

Normally restrictive about releasing information on Iranian hits and damage, Israeli authorities in recent days have sought to educate the public about their dangers, which can persist as unexploded bombs on the ground even after civilians leave shelters.