The IS fighters were killed in a pair of airstrikes targeting positions in Kunar province near the Pakistan border, U.S. Forces-Afghanistan spokesman Col. Sonny Leggett said on Twitter.
"We continue to eliminate ISIS terrorists wherever they hide to protect Afghanistan while honoring U.S.-Afghan-Taliban agreement to reduce the violence," he wrote.
The airstrikes demonstrated that the Islamic State is not covered by the U.S. "reduction in violence" agreement with the Taliban, aimed at producing a peace deal to end the 18-year-old Afghan war.
Should the truce hold for the rest of the week, a signing ceremony instituting a broader deal is to be held Saturday in Qatar.
The Taliban last week committed to refraining from attacking Afghan and U.S. military bases, as well as provincial cities.
The peace deal would lead to the withdrawal of thousands of U.S. troops. In exchange, the Taliban would pledge to begin intra-Afghan talks with various political parties in the country and not harbor terrorists to attack the West.
U.S. President Donald Trump said during a state visit to India Tuesday that a peace deal is "pretty close. We will see what's going on. We have got two days now under our belt without violence, or I guess a minimum of violence, and we'll see what happens."