Militants have killed at least 24 policemen in Egypt's Sinai Peninsula, which has seen an increase in violence since the Egyptian military ousted Islamist Mohamed Morsi from the presidency last month.
The attackers ambushed buses carrying the policemen early Monday near the city of Rafah, along the border with the Gaza Strip.
Also Monday, a lawyer for former Egyptian President Hosni Mubarak said his client will soon be released.
Fareed el-Deeb said an Egyptian court had cleared Mr. Mubarak of corruption charges, stemming from allegations he and his sons embezzled money for presidential palaces.
The claims could not be immediately confirmed by judicial officials. But the French news agency (AFP), quoting judicial sources, reported that Mr. Mubarak will remain in custody on charges in another case.
The 85-year-old Mubarak still faces a retrial on charges he failed to stop the killing of protesters during the popular revolt that swept him from power in 2011.
International concern over the turmoil that has gripped Egypt is growing.
U.S. Defense Secretary Chuck Hagel said Monday he and other officials have had numerous conversations with Egypt's military and that the United States is "reviewing every aspect of our relationship with Egypt."
"This is a very complicated problem. We continue to work with all of the parties to try to help as much as we can - facilitate a reconciliation, a stop of the violence. Our ability to influence the outcome in Egypt is limited."
Hagel refused to specifically say whether the U.S. will suspend military aid to Egypt.
European Union diplomats are set to meet in Geneva Wednesday to review the $6.7 billion in aid it provides to Egypt
On Monday, United Nation's Secretary-General Ban Ki-moon said he was "alarmed" by the ongoing violence and excessive use of force in Egypt. He urged all Egyptians to exercise maximum restraint and to resolve their differences peacefully.
Signs of normalcy returned to Cairo Sunday even as Egypt's interior ministry reported 36 members of the pro-Morsi Muslim Brotherhood were suffocated by tear gas during an attempted prison break in northern Cairo.
Also Sunday, the country's army chief warned that any new violence would not be tolerated. General Abdel Fattah el-Sissi threatened to use force against attacks on government buildings by protesters, but said the army has no intention of seizing power.
He called on Islamic supporters of ousted president Morsi to join the political process, saying "there is room for everyone."
Morsi supporters marched toward the Supreme Constitutional Court in Cairo Sunday, but they canceled two other scheduled protest marches. They claim snipers were planted along the streets.
Protesters gathered for weeks at two protest camps in Cairo to rally against the military's July 3 ouster of the country's first democratically elected president and the installation of an interim government. Many of the protesters called for Mr. Morsi to be reinstated.
Those camps were dispersed with deadly action by security forces last Wednesday. The official death toll from the raids and resulting violence is more than 800, while the Brotherhood says the number is in the thousands.
The interim government held an emergency Cabinet meeting Sunday to discuss whether to ban the Brotherhood, a long-outlawed organization that swept to power in the country's first democratic elections last year.