Three people were killed in an explosion near a security compound in Egypt's Sinai region, near the border with Israel, Reuters reported.
Egypt has been hit by an Islamist insurgency led by Sinai-based militants, who have mainly targeted security forces since last year's army ouster of elected Islamist President Mohamed Mursi. Hundreds of soldiers and police officers have been killed in those attacks.
Medical sources said around 22 others were injured in Sunday's blast.
Security sources said the explosion was due to a rocket targeting North Sinai's main security compound but instead fell in front of a nearby crowded supermarket in Sinai's northern city of Al-Arish. The victims are suspected to all be civilians, according to the sources.
The army ousted Mursi in July of last year after mass protests against his rule and the move was followed by a crackdown on Islamists in which hundreds of street protesters were killed and thousands of Islamist leaders and activists were jailed.
Egypt's newly elected President Abdel Fattah al-Sisi, the former army chief who orchestrated Mursi's overthrow, has promised to fight what he calls terrorism and restore stability to the Arab world's most populous and strategic state.