Three Israeli soldiers and an Egyptian security officer were killed near the countries' border on Saturday, Israel and Egypt said.
A rare incident which the countries said they're investigating jointly.
The Israeli military said an Egyptian police officer shot and killed two soldiers while they secured a military post at the Egyptian border early on Saturday.
It said the officer and a third Israeli soldier were then killed in a confrontation inside Israeli territory hours later.
Egypt's military said that the three Israeli and one Egyptian security personnel had been killed in an exchange of fire as the Egyptian security officer chased smugglers across the frontier.
Israel evacuated one person wounded in the shooting to hospital
The Israeli military said it was unclear how the Egyptian officer crossed the border fence and soldiers were searching the area to rule out additional assailants.