A makeshift bomb went off in Semouha district in eastern Alexandria early Monday but no casualties were reported.
The bomb was planted near a telecommunications store.
Security forces sealed off two main streets in the area in search for other explosives.
The Mediterranean city was the scene of three bomb explosions on Sunday that left one dead and nine wounded.
Elsewhere, a police sergeant was wounded when unidentified men opened fire at Franciscan Church in Beheira.
The gunmen driving a Jeep fired a shower of bullets at policemen securing the church and fled away.
Police launched a manhunt to arrest the culprits.