The army managed to kill seven of the extremists during the firefight, but did not give any further information on the army's own casualties, according to a statement by Col. Tamer Rifai.
Two other officers in the area who gave a more detailed account said the officer and all the other 14 troops had been killed.
The attack involved some 200 fighters storming in from nearby olive groves, hitting the outpost with sustained heavy gunfire before entering the compound, which is near an airport, they said. The men seized weapons and then fled back through the groves, they added, speaking on condition of anonymity as they weren't authorized to brief journalists.
The army has for years been battling a long-running insurgency in North Sinai that is now led by an Islamic State affiliate. The fighting intensified after the military overthrew an elected but divisive Islamist president in 2013.
Authorities heavily restrict access to the northern Sinai, making it difficult to verify claims related to the fighting.