The U.S. Army soldier accused of killing 16 Afghan men, women and children in a house-to-house shooting rampage could face the death penalty, Defense Secretary Leon Panetta said.

Panetta spoke to reporters as he flew to the Central Asian nation of Kyrgyzstan for high-level talks Tuesday.

Hundreds of Afghans took to the streets Tuesday to protest the killings as the Taliban threatened to behead "Americans anywhere in the country."