Egypt's military chief of staff Sami Enan headed to Sinai on Friday to probe the deaths of policemen killed by Israeli gunfire the previous day, a military source said.

"Enan will head a committee that will investigate the deaths of soldiers by Israeli gunfire,"  the source said.

Egyptian Security sources said on Friday that five policemen, including an officer, were killed on the previous day as Israeli and Egyptian troops combed the border area following attacks in Israel that killed eight.

There have been conflicting reports from the military and police about how the Egyptian policemen died.

A military official told the official MENA news agency on Thursday night they were accidentally killed by Israeli helicopter fire aimed at fleeing militants.

But on Friday, the state-owned Al-Ahram newspaper quoted a military official as saying the policemen were killed by gunmen trying to slip in from Israel.

Enan's visit was announced shortly after another policemen was declared dead after a border gunfight on Friday, which left one of his comrades gravely wounded with a bullet in the head.

The military said on Thursday night that it was combing the border after gunmen, who witnesses said were dressed in Egyptian military uniforms, opened fire on Israeli buses and cars.

Israel said the militants had come from the Gaza Strip, and slipped into Israel through neighbouring Egypt's Sinai.

The attacks appeared to have caught Egypt's security forces by surprise, as they engage in a sweeping week-long crackdown on Islamist militants in the peninsula.