A roadside bomb killed seven Egyptian soldiers and wounded four in the restive Sinai Peninsula on Sunday, security officials said.
The bomb exploded next to an armoured vehicle guarding a gas pipeline in north Sinai, the officials said.
Militants have killed scores of policemen and soldiers in the rugged peninsula since the military overthrew Islamist president Mohamed Morsi in July 2013.
A military official said first responders were still assessing the casualties.
The attack came three days after a similar bombing killed two policemen in the north Sinai provincial capital of El-Arish.
Militants killed 17 policemen in Sinai in two bombings in September and later released footage of the attacks.
Those attacks were claimed by Ansar Beit al-Maqdis, the most active militant group in Egypt. It tried to assassinate the interior minister in Cairo last year with a car bomb.
The group has expressed support for Islamic State jihadists in Iraq and Syria, although it has not formally pledged its allegiance.
President Abdel Fattah al-Sisi, the army chief who overthrew Morsi and later won elections, has pledged to eradicate the militants.
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The military has said it killed at least 22 militants in October, including a local Ansar Beit al-Maqdis commander.
The group itself has acknowledged the arrest or deaths of its cadres, but so far the army has been unable to quell the militants despite a massive operation in which it has deployed attack helicopters and tanks.
The militants sometimes operate openly in north Sinai, setting up impromptu checkpoints and handing out leaflets.
They say they target policemen and soldiers to avenge a bloody police crackdown on Islamists after Morsi's overthrow, which killed hundreds in street clashes and imprisoned thousands.
Squeezed by the police crackdown, pro-Morsi protests have grown smaller and less frequent, but disaffected Islamists are thought to be increasingly drawn to militancy.
The government has declared Morsi's Muslim Brotherhood group a terrorist organisation after blaming it for an attack conducted by Ansar Beit al-Maqdis.
The group, whose name means Partisans of Jerusalem in English, formed after the 2011 uprising that overthrew veteran strongman Hosni Mubarak and ushered in a period of lawlessness, especially in the sparsely populated Sinai peninsula.
They initially focused their attacks on neighbouring Israel, firing rockets and conducting two cross border raids that killed a number of Israeli civilians and soldiers.
Ansar Beit al-Maqdis's leaders are believed to be Bedouin and some of its members had fought in Syria alongside jihadists before returning to Egypt.