At least 24 Egyptian police officers have died in an ambush in the Sinai Peninsula.
The attack took place on August 19 near Rafah on the Gaza Strip border.
Militants have stepped up attacks in Sinai, mainly targeting the Egyptian security forces, since the military ousted and detained Islamist President Muhammad Morsi on July 3.
The ambush comes after 36 detainees died in a police van on the outskirts of Cairo on August 18.
Police say the victims suffocated after tear gas was fired into the van when detainees tried to escape. However, Morsi's Muslim Brotherhood has accused security forces of intentionally killing the detainees.
UN Secretary-General Ban Ki-moon condemned the violence in Egypt and called for dialogue.
"I'm alarmed by ongoing developments and the widespread outbreak of violent protests and excessive use of force," Ban said. "I strongly condemn attacks on churches, hospitals, and other public facilities."
Meanwhile, a lawyer for jailed former President Hosni Mubarak said his client may be freed from custody this week, after he was cleared on August 19 of one charge of corruption.
It is the third charge the court has cleared the former president of since April, leaving Mubarak with just one corruption charge remaining against him.
Mubarak's lawyer, Farid al-Dib, is expected to try to refute the last charge by arguing that Mubarak has already paid back the more $600,000 worth of gifts he is accused of receiving from his minister of information, and that therefore he should be set free immediately.
Mubarak, along with his interior minister, was convicted and sentenced to life in prison last year for failing to stop the killing of protesters in the revolt that swept him from power in 2011.
He still faces a retrial in that case after appeals from the prosecution and defense, but this would not require him to stay in jail until his court date.
EU To Meet, 'Extremely Worried'
Meanwhile, EU foreign ministers are due to hold emergency talks about Egypt on August 21.
The decision comes after senior diplomats from the 28 EU member states met on August 19 in Brussels for a preparatory round of talks about the Egyptian crisis.
The presidents of the European Council and European Commission, Herman Van Rompuy and Jose Manuel Barroso, said in a joint statement on August 18 that "recent developments in Egypt, and more particularly the violence of the last days, are extremely worrying."
They added, “It is crucial that violence ends immediately."
Brussels has warned that the bloc will "urgently review" ties with Cairo in the wake of the killing of at least 830 people last week in clashes between security forces and Morsi supporters.
Bernardino Leon, the European Union's special representative for the southern Mediterranean region, said on August 19 in Brussels that the EU could impose an arms embargo on Egypt.
"I know that this is one of the possibilities that have been evoked by foreign ministers and undoubtedly they will discuss it on the basis of these statements next Wednesday," Leon said.
The European Union is also Egypt's biggest trading partner, with a trade volume of almost 24 billion euros in 2011 (then $34.5 billion).
The EU and its member states last year pledged a combined 5 billion euros ($6.7 billion) in loans and aid for Egypt.
In Washington, the U.S. State Department said that a review on military, security and economic assistance to Egypt was still ongoing and ajustments would be made "as needed."
Egypt receives $1.3 billion annually in military aid from the United States.
With reporting by AP, AFP, and Reuters