Unidentified assailants shot dead a police officer Sunday and injured four others when they opened fire on a security checkpoint in Alexandria, the third attack against policemen in the city this month. Militants driving a car opened fire on a security checkpoint in al-Montaza district, killing one policeman and injuring four others, security sources said. Another two policemen were shot dead yesterday by unidentified assailants on a motorbike during their security shift in Giza. Armed attacks against police and army forces broke out in Egypt after the ouster of former president Mohamed Morsi in July 2013. The attacks were mainly targeting the Sinai peninsula, but recently moved to the capital and other provinces.