(CNN) -- Explosions hit two metro stations and a courthouse in Cairo on Wednesday, injuring at least four people, state media reported.
Two blasts went off at two different metro stations during the early morning rush hour, Egypt's state-run Al-Ahram website said.
The first explosion in the metro was caused by an improvised bomb at Shubra station, Al-Ahram reported, citing Interior Ministry spokesman Abdel-Fattah Othman. The second blast came from a "sonic explosive" in a trash can at Ghamra station, it said.
The ministry spokesman denied earlier reports that explosions had gone off at more than two stations.
Metro stations were reported to have been brought to a complete standstill as the ministry has declared a maximum alert.
Another blast struck near the Heliopolis courthouse in eastern Cairo, Al-Ahram reported, citing eyewitnesses and local media.
There was no immediate claim of responsibility for the blasts.
Militants in Egypt have stepped up attacks since the military's ouster last year of former President Mohamed Morsy, Egypt's first democratically elected top leader.
Last month, a spate of deadly explosions struck around the country, including one near a Cairo metro station.