Twin car bombs in Giza on Wednesday were targeting electricity pylons, security sources told Al-Ahram Arabic news website.
One bomb accidentally detonated in a car, killing three suspected militants, while the second was detected before it went off. Security forces arrested and interrogated the suspected militant inside the second vehicle, a few hours after the first bomb exploded.
Investigations showed that the assailants were on their way to attack the high pressure towers linking the electricity production unit to the Al-Saf district.
A statement on the official Facebook page of the Interior Ministry said the first bomb exploded instantly killing two suspected militants, while the third was transferred to a local hospital and later died of his wounds. The car was also severely damaged.
Egypt has witnessed an upsurge in attacks, mainly targeting security forces and installations, since the ouster of Islamist president Mohamed Morsi last year.
Recently, unknown assailants have frequently targeted electricity substations, towers and circuits in several parts of the country, already plagued by recurrent summer blackouts and a severe energy crunch.
On Sunday, an electricity pylon in Qalioubiya governorate, north of Cairo blew up, damaging the trestles of the 500kv tower and causing it to collapse. A state electricity company official said the explosion was the seventh in two weeks.
Another explosion last week blew up an electricity pylon feeding West Cairo and a district north of the capital.