Two bombs were found in different terminals of Cairo's main airport on Tuesday, shortly after a homemade bomb exploded in a busy area in the Egyptian city.
Airport authorities raised the security levels after the police detected two bombs using electronic devices and defused them. Authorities are now examining CCTV footage to identify who planted the bombs.
The bomb that went off in central Cairo near Tahrir Square did not cause casualties, and the intent behind the blast was unclear.
The blast comes a day after an Egyptian court upheld the death sentence for 183 supporters of the Muslim Brotherhood for their role in an attack on a Cairo police station in 2013.
Egypt has been on edge over the last few days as violence gripped its norther Sinai province. Islamist militants targeted security officers and killed about 30 in a series of attacks, while clashes with the army left several dead, including women and children.
President Abdel Fatah al-Sisi blamed the Sinai attacks on the Muslim Brotherhood.