Three Israeli soldiers have been killed by an Egyptian security officer in exchanges of fire on the Israeli side of the border.
The armed forces of both countries say they are jointly investigating the unusual incident.
Egypt says its officer crossed into Israel while chasing drug traffickers.
The Israeli military has said the shootings were assumed to be connected with a drug smuggling operation it had thwarted overnight.
According to the army, two Israeli soldiers – a man and woman – posted in a remote spot along the border were shot dead early on Saturday morning.
Their bodies were discovered after a senior officer was unable to contact them by radio.
Hours later, after a search operation, the alleged attacker was encircled and there was a shootout, the Israeli military says.
A third soldier was killed, along with the gunman, who it said was an Egyptian policeman.
Another soldier was wounded in that exchange.In a vaguely worded statement, the Egyptian military said that its security officer was pursuing drug smugglers and that a shooting led to the Israeli deaths.
It also conveyed “sincere condolences” to the families of the victims.
The Israeli military says contraband worth about $400,000 was seized by its forces during the overnight operation against smugglers.
Soldiers are continuing to search in the area for others that may have been involved, the army says. It is not clear how the policeman managed to enter Israel from Egypt.
Israeli media say the attacks happened between Mount Harif and Mount Sagi – which lie in the Negev desert, about half-way between the Mediterranean coast and the Red Sea Egyptian resort of Eilat. (BBC)