Another three soldiers were wounded in the attack on the Al-Reesa checkpoint just south of North Sinai's main town of El-Arish, the officials told AFP.
Attacks on the army and police have increased since the army's July 3 ouster of Islamist president Mohamed Morsi and a subsequent crackdown on his supporters and members of his Muslim Brotherhood.
Militants have launched a series of brazen attacks this week, after at least 57 people were killed in clashes between security forces and Morsi supporters on Sunday, most of them in Cairo.
In the Suez Canal city of Ismailiya, gunmen killed six soldiers in an attack on an army patrol.
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And in Cairo, unknown assailants fired rocket-propelled grenades at communication satellite dishes, damaging one.
Morsi, who ruled as Egypt's first democratically elected president for just one year, was overthrown in July by the military with massive popular support.
Since then, the army-installed authorities have carried out a massive crackdown on Morsi supporters.
Hundreds were killed when security forces dispersed pro-Morsi protest camps in August, and at least 2,000 Muslim Brotherhood members are behind bars.