Egypt lodged a formal protest with Israel on Friday over the killings of three members of its security forces during an Israeli raid to hunt down attackers who had killed eight Israelis in south Israel on Thursday.
An Egyptian army officer and two other security men died when Israeli forces launched an operation to pursue militants who had launched attacks on the south Israel border. Seven other security men were injured.
"Egypt has filed an official protest to Israel over the incidents at the border yesterday (Thursday) and demands an urgent investigation over the reasons and circumstances surrounding the deaths of three of Egypt's forces," the Egyptian army said in a statement after a meeting of the ruling military council.
The circumstances of the deaths were not immediately clear. The army said it had launched its own investigation.
Israel said the militants had come from the Hamas-run Gaza Strip through Sinai. Egyptian security forces have been conducting their own operation against militants in Sinai.
An Egyptian policeman died in clashes with gunmen in the el-Kuntilla region near the Israeli border in central Sinai on Friday, security sources said.
Two other policemen were injured in heavy clashes in the area, where Egyptian security forces have been hunting down militants behind a string of recent attacks on Egyptian installations and a pipeline used to export Egyptian gas to Israel and Jordan.
Thursday's attack represented a major test for ties between Israel and Egypt following an uprising that ousted President Hosni Mubarak and strengthened forces hostile toward Israel.
A cabinet spokesman said the government of Prime Minister Essam Sharaf also planned to hold an emergency meeting later on Friday to assess the situation in Sinai. The spokesman said members of the ruling military council and Egyptian intelligence would attend.
Israeli Defence Minister Ehud Barak said the border incident "reflects the weakening of Egypt's hold in the Sinai and the broadening of activities by terror elements," angering many Egyptians.
Sinai governor Khaled Fouda rejected Barak's comments, saying "we refute such statements and have increased security patrolling and checkpoints in Sinai."
Dozens of Egyptians demonstrated outside the Israeli embassy in Cairo following Friday prayers, denouncing the Israeli attack on the Egyptian border.
Presidential candidates Amr Moussa and Hamdeen Sabbahi also denounced the killing of three Egyptian security men.
"Israel must realize that the day when Egypt's sons are killed without an appropriate and strong reaction are over," Moussa said in comments on his web site.
Sabbahi also called for a deterrent response.
Hours after Thursday's attack, Israel struck the Popular Resistance Committees, an armed faction that often operates independently of Gaza's Hamas rulers. The Israeli military said the group was behind the border attack -- a charge denied by the faction.
The group said its commander, Kamal al-Nairab, his deputy, Immad Hammad, and three other members were killed in the Israeli air strike on a home in the southern Gaza town of Rafah.
Israeli aircraft also struck Hamas outposts in Gaza and Palestinians fired rockets into southern Israel on Friday as violence escalated.