The White House condemned a wave of bombings in Cairo on Friday and urged all sides in Egypt's political turmoil to avoid violence.
"These crimes should be investigated fully and the perpetrators should be brought to justice," White House spokesman Jay Carney told reporters after bomb attacks killed six people and underscored the struggle by Egyptian authorities to tame an Islamist insurgency.
Carney also called for an end to violence surrounding Egypt's unrest. Clashes in the capital and several other cities between demonstrators and security forces raised tensions on Friday.
"It should be clear to all Egyptians that violence has not and will not move Egypt's political transition forward," he said.