Egypt's Churches have condemned the killing of policemen ambushed in the country's western desert on Friday and called for the terrorists to be brought to justice.
Egypt's security forces suffered one of their heaviest attacks after militants firing rockets and detonating explosives hit a police operation.
Reports about the number of casualties were confused, with numbers varying from 52 to only 16, the official figure given by Egyptian authorities.
Egyptian authorities on Saturday said two police operations were moving in on a suspected militant hideout on Friday when one of the patrols came under fire from heavy weapons in a remote area around 135 km southwest of Cairo.
The interior ministry said 16 police were killed in that part of the operation, and 13 more were wounded. At least 15 militants were also killed in the gun fight. The statement did not give details on any casualties in the other police patrol.
The Orthodox church, led by Pope Tawadros, offered condolences to the families of the killed and prayers for the recovery of the injured. It stressed its support for Egypt's battle against terrorism, saying: 'We will always remain supporters of all efforts and sacrifices of the army and police in their fights against terrorism.'
The head of Egypt's Evangelical Church, Rev Dr Andrea Zaki, also expressed the Church's support for the country's political leadership. According to Egypt Today he offered prayers for Egypt's leadership, people and security forces.
No group made any claim or statement about Friday's operation not far from the capital. But most of the fighting so far between militants and security forces has been in northern Sinai, where an Islamic State affiliate operates.
Security sources earlier said the police had been hunting hideout of the Hasm Movement, an Islamist militant group blamed for attacks on judges and police around the capital.
That group has in the past only carried out mostly small operations since it emerged last year. Egyptian authorities say it is the armed militant wing of the Muslim Brotherhood, an Islamist group it outlawed in 2013. Most of its leadership has been jailed in a crackdown under Sisi.
Since Sisi came to power, hundreds of troops and police have been killed in often sophisticated attacks by militants in the northern Sinai region, where Ansar Bayt al-Maqdis group pledged allegiance to Islamic State in 2014.
Last Sunday, at least 24 militants and six soldiers were killed in attacks on military outposts in North Sinai, when more than 100 militants repeatedly attacked security outposts south of the border town of Sheikh Zuweid.
Attacks have mostly hit police and armed forces, but militants have also extended their campaign outside the Sinai, targeting Egypt's Christians with bomb attacks on churches in Cairo and other cities.
Additional reporting by Reuters.