A bomb exploded at a Cairo police station on Saturday, causing no injuries, state media reported.
In a separate incident, explosives were found on the railway line between the cities of Suez and Ismailia, state news agency MENA news agency said. They were defused by experts.
Train traffic on the line was suspended pending an army search of the area, state newspaper Al-Ahram said, quoting an army official.
Egypt has been gripped by unrest since the army overthrew the country's first freely elected president, Islamist Mohamed Morsi, on July 3.
The Egyptian interior minister survived an assassination attempt unscathed on Thursday when a car bomb blew up next to his convoy, which he said was the start of a likely wave of violence against the military-installed government.
An attack on the Suez Canal would hammer Egypt's economy, which depends heavily on revenue from the 192-km (120 mile) waterway.
In the North Sinai, army helicopters carried out air strikes on suspected militant outposts near the towns of Sheikh Zuweid and Rafah on Saturday, MENA reported, quoting witnesses.