A police officer and a police conscript were killed when armed assailants attacked a security checkpoint on Cairo's ring road on Thursday, Ahram's Arabic website reported. The assailants, who were in two separate cars, opened fire on the checkpoint and fled. Police are investigating. Clashes between police and protesters supporting ousted president Mohamed Morsi on Wednesday have left 638 dead so far – according to health ministry figures – and thousands injured. Clashes ensued after police dispersed two sit-ins by Morsi's supporters in Cairo. The angry protesters attacked police stations and government offices in reaction to the violent crackdown by police. Another drive-by shooting by unknown assailants on the Cairo-Ismailia highway killed an army officer and conscript on Wednesday. http://english.ahram.org.eg/News/79157.aspx