A bomb has wounded five policemen near a Cairo university, and four people were hurt after an explosion at a train station, security officials say.
Egypt has been hit by a wave of bombings and shootings since the military ousted Islamist president Mohamed Morsi in July 2013.
The five policemen, including two officers, were hurt when a bomb exploded at a small post near Helwan University in southern Cairo, security officials said.
But the interior ministry said assailants in a speeding car threw a bomb at the policemen near the university, wounding four officers and a conscript.
Egypt is fighting an Islamist insurgency that has killed scores of policemen and soldiers, mostly in the Sinai Peninsula.
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But militant groups have also staged attacks in other parts of the country, including Cairo.
They say they are acting in retaliation to a brutal government crackdown targeting Morsi's supporters that has left at least 1400 people dead since his ouster.
A militant group called Ajnad Misr (Soldiers of Egypt) claimed Thursday's bombing on the police in a statement posted on Twitter.
"As a quick response to security forces that target university students... a group of heroes targeted the security force that besiege Helwan University," it said.
The group, which called on youth to "take up arms against security forces," said it was targeting officers in the police but warned that it did not rule out attacks on the lower ranks as well.
Meanwhile on Thursday, four people were injured in a stampede at the capital's Ramses station after a blast inside a compartment of a train that pulled in from the Nile Delta, security officials said, adding that the blast was caused by a "sound bomb".
