Egypt protested to Israel on Friday and demanded a probe into the deaths of its policemen a day earlier on the Israeli border as Israeli troops pursued militants behind deadly attacks, the official MENA news agency reported.
"Egypt filed an official complaint with Israel following yesterday's deaths at the border between Israel and Egypt," the agency reported.
"Egypt has demanded an urgent probe into the circumstances of the deaths and injuries of Egyptian forces' members inside our borders," the agency quoted a military official as saying.
Earlier, military sources said Sami Enan, the military chief of staff, visited Sinai on Friday to look into the deaths and raise troop morale.
A military official told MENA that "Egyptian forces were conduction a comprehensive assessment on its side of the border to determine the reasons for the deaths and injuries of Egyptian forces."
He said the military would take measures "to ensure that will not happen in the future."
The military has been conducting a week-long operation in the peninsula to uproot Islamist militants behind attacks on police and a gas pipeline to Israel.
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Security forces told AFP that five policemen, including an officer, were killed at the border on Thursday hours after gunmen believed to have crossed into Israel from Egypt opened fire on buses and cars, killing eight.
The military told the official MENA news agency on Thursday that two policemen were killed when an Israeli aircraft opened fire on the fleeing militants, catching the policeman in the line of fire.
But military and security officials later said the policemen were killed in a clash with gunmen as they tried to enter Egypt. The military has promised to issue a statement clarifying its contradictions.
Another policeman was killed on Friday in an exchange of gunfire with armed men near the border with Israel, security officials said. One of his comrades was gravely wounded with a shot in the head.
Eight Israelis were killed in a string of attacks in the south of the country Thursday, prompting a series of Israeli air strikes targeting a Palestinian Gaza Strip group it said was responsible.
Israel said the Egyptian military, in charge since a revolt ousted president Hosni Mubarak in February, was looking control of Sinai, and Washington urged it to do more to secure the peninsula.
Witnesses said the gunmen who attacked buses and cars north of the town of Eilat were dressed in Egyptian military fatigues and Israeli officials said they had slipped into the country through its porous borders with Israel.
MENA reported on Friday that the Ouja commercial border crossing with Israel would be closed indefinitely.