As of Wednesday night, the Egyptian military is "100% in control" of the situation in the northern Sinai, an Egyptian armed forces spokesman told state-run news agency MENA.
At least 17 security forces, including four police officers, were killed in the attacks, the Egptian military said on its Facebook page.
The spokesman for the Egyptian military said 100 terrorists had been killed.
The Islamic State in Iraq and Syria was known exclusively for its activities in those two war-torn countries until recently.
But it has claimed responsibility in the last week for a drumbeat of attacks in a range of countries: the deadly bombing of a mosque in Kuwait on Friday, the horrific beachfront killings in Tunisia
the same day, and now five coordinated military attacks in Egypt.
A deadly claim on Twitter
ISIS claimed responsibility for Wednesday's attacks in statements posted on Twitter.
Earlier Egypt's state-run Al-Ahram online media outlet reported 20 soldiers had been killed and 30 others injured, but the death toll was later revised downward.
A spokesman for the Egyptian military, Mohammed Samir Abdelaziz Ghaneem, said the clashes between ISIS and Egyptian soldiers were continuing. Egyptian military forces were continuing to chase the terrorists, he said.
Ghaneem posted on his Facebook page: "70 terrorists attacked 5 checkpoints simultaneously in North Sinai."
The Sinai borders the Mediterranean Sea to the north and Israel to the east. It is the only part of Egypt that lies in Asia rather than Africa.
The toll: 38 dead in Tunisia, at least 27 in Kuwait
Also Wednesday, ISIS released a video in which militants threaten to attack leaders of Hamas in Gaza. The three armed men call Hamas' leaders "apostates." In the video, given the English title of "A Message To Our People In Jerusalem," ISIS calls on residents of Gaza to turn on Hamas.
The nearly 17-minute video is a rare threat to Hamas, a Islamist political movement that controls Gaza.
It is also the latest sign of ISIS trying to broaden its influence.
On Friday, a gunman with apparent ties to ISIS roamed a Tunisian beachfront, shooting 38 people to death and leaving others wounded. Police shot and killed the gunman.
And in Kuwait that same day, a bomber also apparently linked to ISIS blew himself up inside a mosque during Friday prayers, killing at least 27 people.
ISIS' expanding reach is worrying officials concerned about keeping their populations safe. The interior ministers of Germany, Britain and France traveled to Tunisia this week to meet with that country's interior minister.
They pledged continued work on finding ways to thwart attacks and, in the words of British Home Secretary Theresa May, "to fight against this perverted ideology that is causing this death and destruction."