Egyptian security officials said suspected Islamic militants ambushed police in the northern Sinai Peninsula, killing three Egyptian policemen.

The gunmen pulled in front of a police vehicle in an unmarked truck in the area’s main city of El-Arish, before standing up on the truck bed and opening fire, the officials said. They then raised a black flag associated with jihadis and shouted “God is great.”

Intelligence officials said the suspects then sped off.

The head of security in northern Sinai, Ahmed Bakr, confirmed that three policemen were killed in the Saturday attack.

The incident was the most serious since terror cells killed 16 Egyptian security personnel in an attack near the Egypt-Israel-Gaza border in August. Since then, the government of President Mohammed Morsi has moved to try to quash the cells in the unstable Sinai Peninsula, which borders the Gaza Strip and Israel.

In the August attack, the terrorists who killed the Egyptian troops then smashed into Israel at the Kerem Shalom border crossing, before the Israeli Air Force was able to get a clear shot and blow up the Egyptian Army armored vehicle the gunmen had commandeered.