A roadside bomb near Egypt's second largest city Alexandria killed a bystander and injured two others on Tuesday, while authorities defused two more explosives at Cairo International Airport, officials said.

The latest reports are part of recent spike in small bombs being planted around Egypt. Many of the devices have been so-called flash-bang grenades, designed to sow panic but cause minimal damage or casualties. The larger and deadlier bombs have been targeted almost exclusively at members of the Egyptian police and army.

There are rarely individual claims of responsibility, but Islamic militant groups have vowed to target police and military troops to avenge their crackdown on Islamists in the wake of the ouster of Islamist President Mohammed Morsi in 2013.

Reflecting the increased public fear and awareness, a popular smartphone application designed to provide information on traffic jams started a new service last week titled "Where is the bomb" to alert commuters of reports of roadside explosives.

Tuesday's roadside bombing was a rare incident of a civilian killed by these rudimentary explosives. The officials said the bomb was targeting a police patrol driving in the beachfront town of Agamy, on the western outskirts of Alexandria. The bomb went off, apparently detonated remotely, as the vehicles moved — injuring a street peddler, his son and a bystander. The bystander later died of his wounds, the officials said.

In Cairo, officials said a bomb was planted in the Cairo International Airport arrival hall of the terminal hosting EgyptAir. Another was planted near a police patrol location in the airport's parking lot. Both were defused. The officials said the bombs appeared to be controlled remotely by mobile phone. Airport officials said flights were not affected.

In another incident, a flash-bang grenade planted inside an electrical box in an open-air commercial arcade in downtown Cairo exploded, panicking passers-by, but causing no injuries.

The officials spoke on condition of anonymity because they were not authorized to speak to journalists.