One killed as bombs explode in Cairo, Alexandria

One Egyptian was killed and three wounded when a bomb blast struck a residential neighbourhood in Alexandria on Tuesday.

A 12-year-old boy were among those injured in the explosion which occurred on the outskirts of the city and targeted a mobile checkpoint, police said.

Hours earlier, a small bomb hidden in an electrical transformer exploded Tuesday in downtown Cairo. No casualties were reported, security officials said. 

The blast happened around 9AM (7AM GMT) on a street close to Tahrir Square - the site of mass protests in the 2011 revolt that ousted autocrat Hosni Mubarak.

There was no immediate claim of responsibility.

Airport security officials said Tuesday that two "sound bombs" were also found near a parking lot at Cairo International Airport, adding that the devices were later defused.

One of them was found in a gift bag outside Terminal Three. After airport security officials reported it to the police, the second bomb was found by sniffer dogs under a policeman's car outside the terminal.

Since the army toppled Islamist president Mohamed Morsi in July 2013, scores of policemen and soldiers have died in militant attacks, mostly in the Sinai Peninsula.

The militants say the killings are to avenge a deadly crackdown on Morsi supporters since his overthrow.

Egyptian authorities have often blamed the outlawed Muslim Brotherhood, the group from which Morsi hails, for the attacks which have mostly targeted.

The Brotherhood denies the accusations and says it is committed to peaceful activism.