Three army officers and a soldier were killed in Egypt's Western Desert on Wednesday when an explosive belt seized from Islamist militants went off, the military said in a statement.
The Egyptian Air Force was conducting reconnaissance over the Bahariya Oasis area when it discovered and fired on two four-wheel drive vehicles transporting militants.
As the Egyptian Army was clearing the area and dealing with the weapons and equipment the militants left behind, an explosive belt went off, killing three officers and a soldier.
Egyptian security forces have been battling Islamic State, which killed hundreds from the military and police.
The insurgency was until recently concentrated in the remote Sinai Peninsula but the militants have extended their campaign to other parts of Egypt.