Airport authorities in Cairo tightened security on Tuesday after two bombs were discovered near the terminal, according to security officials speaking on condition of anonymity as they were not authorized to speak with journalists.

News agency DPA reports that the first device was found inan arrivals hall at the airport's Terminal 1, while the second was found beside a police commander's car. At least one of the bombs was set up to be detonated via mobile phone. Both devices were defused by security forces overnight to Tuesday and video footage was being reviewed to see who had planted the bombs.

Another bomb exploded on a street near Tahrir Square in downtown Cairo on Tuesday.

"A small bomb hidden in a roadside electrical transformer went off, damaging the transformer but causing no casualties," a police officer told news agency AFP.

Egyptian state news agency MENA quoted Cairo security head Khaled Youssef as saying the device was a sound bomb.

No-one immediately claimed responsibility for planting either bomb.

There have been frequent bomb attacks in Egypt since mid-2013, when elected Muslim Brotherhood-backed President Mohammed Morsi was ousted by the military. The attacks have ranged from suicide bombings targeting soldiers and police, to frequent small blasts from homemade devices targeting civilian institutions and public places in the capital.

Last week, a jihadist group claiming loyalty to the "Islamic State" group claimed responsibility for a series of coordinated attacks which killed dozens of security force members and civilians in the North Sinai region.

se/msh (Reuters, AP, AFP, dpa)