Unidentified assailants threw an explosive device at a check point in Qalioubiya on Tuesday morning, Al-Ahram Arabic news website reported.
The attack in Abu Zabal caused damage to nearby walls and building but caused no injuries.
In Upper Egypt's Fayoum an improvised bomb exploded near a court building. No deaths or injuries were reported.
Militants have targeted police and soldiers, killing hundreds in attacks since the ouster of Islamist president Mohamed Morsi in 2013.
Over 200 militants have been killed by security forces so far, according to the latest official figures.
Dozens of bombs were defused on Sunday, the fourth anniversary of Egypt's 2011 revolution, police said.