The Egyptian military has said that militants killed one officer and 10 soldiers during an attack on a water facility in the Sinai Peninsula. Five more personnel were wounded in the incident, it said.
In a Facebook statement posted on Saturday, a military spokesman said the attackers were being pursued and were now under siege in a remote area of Sinai. The military did not say when the assault took place.
Those killed and wounded belonged to an army contingent in the area, the military said, but it gave no further details. The death toll suggests that the militants attacked in force.
Egyptian President Abdel Fattah El Sisi offered his condolences to the families of the victims and wished the wounded a full and speedy recovery.
"These treacherous attacks will not undermine the resolve and will of the sons of this nation and its armed forces to uproot terrorism," he wrote on his Facebook page.
The UAE's Ministry of Foreign Affairs and International Co-operation said it affirmed the UAE's strong condemnation of such criminal acts, and its permanent rejection of all forms of violence aimed at destabilising security and stability.
The number of casualties is one of the highest death tolls among Egypt's security forces in months and is bound to provoke a strong response from the government.
No group claimed responsibility for the attack. The militants are known to be led in northern Sinai by a local branch of ISIS.
Egyptian soldiers and police, often backed by fighter jets and helicopter gunships, have been fighting militants in the region for years.
In 2018, the government launched a major offensive against the rebels, dislodging militants from most of their strongholds in northern Sinai, close to the Israel and Gaza border.
Mr El Sisi said last month that 3,277 service members from the army and police had been killed fighting militants since 2013. More than 12,000 have been injured, he added.
The number of attacks blamed on militants surged after the 2013 removal of Islamist president, Mohammed Morsi, amid a popular uprising against his divisive one-year rule. However, their frequency was dramatically reduced after the 2018 offensive.
"We have settled the issue there, but the cost was very high," Mr El Sisi said on April 27. "We will only declare the end of terrorism in Sinai when we have cleared all the roadside bombs there."
However, isolated, low-intensity attacks have continued, including the kidnapping and killing of civilians suspected of working for the military or members of tribes that have openly sided with the government. There have also been attacks on small but remote police and army outposts.
Last week, suspected militants blew up a natural gas pipeline in the northern Sinai town of Bir Al Abd, starting a blaze but leaving no casualties.