A bomb wounded five policemen near a Cairo university Thursday, and four people were hurt in a panicked crush after an explosion at a train station in the Egyptian capital, security officials said.
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.
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 1,400 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.
The group has claimed several previous attacks on security forces in Cairo, including one near Cairo University last month that wounded nine people.
Police have tightened security in and around universities across Egypt, where students supporting Morsi still stage regular protests.
During the past academic year, at least 14 students were killed in clashes with security forces on university campuses -- the last bastions of pro-Morsi protesters.
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."
Amid a growing number of attacks on public transport, 16 people were injured in panic sparked by an explosion at a Cairo metro train station on November 13.
A week earlier, a bomb on a train north of the capital killed two policemen and two passengers.
In other developments, in the delta province of Sharqiya, three empty state transport buses were set on fire in separate incidents by unknown people, the officials said.