Islamic State (IS) militants have launched a wide-scale coordinated assault on several military checkpoints in Egypt's North Sinai in which 50 people were killed, the largest attack yet in the insurgency-hit province.

Egyptian army F-16 jets and Apache helicopters strafed the region that lies within the Sinai Peninsula, a strategic area located between Israel, the Gaza Strip and the Suez Canal.

It was the second high-profile attack in Egypt this week. On Monday, the prosecutor-general was killed in a car bombing in Cairo.

The attacks raise questions about the government's ability to contain a Sinai-based insurgency that has already killed hundreds of police and soldiers.

IS's Egyptian affiliate, Sinai Province, claimed responsibility for the Sinai attacks.

The army had said five checkpoints were attacked by about 70 militants and soldiers had destroyed three landcruisers fitted with anti-aircraft guns.

The exact breakdown of identities of those killed was not immediately clear.

Security sources said militants were surrounding a police station in the town of Sheikh Zuweid and had planted bombs around it to prevent forces from leaving.

They also said the militants had planted bombs along a road between Sheikh Zuweid and an army camp to prevent the movement of any army supplies or reinforcements. The militants managed to seize two armoured vehicles and boxes filled with weapons and ammunition, the sources said.

The insurgency based in the Sinai is seeking to topple the Cairo government and has managed to defy one of the toughest security crackdowns in Egypt's history.

It has intensified since 2013, when then-army chief Abdel Fattah al-Sisi removed President Mohamed Morsi, an Islamist, after mass protests against his rule.

Sinai Province said it had attacked more than 15 security sites and carried out three suicide bombings.

IS had urged its followers to escalate attacks during the Islamic holy month of Ramadan which started in mid-June, though it did not specify Egypt as a target.

In late April, the army extended by three months a state of emergency imposed in parts of Sinai since October after 33 security personnel were killed in an attack claimed by Sinai Province.

The army has taken several measures to crush the insurgency. Aside from bombardments in the region, they have destroyed tunnels into the Palestinian-ruled Gaza Strip and created a security buffer zone in northern Sinai.

The army was also digging a trench along the border with Gaza in an effort to prevent smuggling.

The measures have stoked resentment among some residents, who say they rely on the smuggling trade through the tunnels and complain of neglect by the state.

Under the terms of Egypt's 1979 peace accord with Israel, the Sinai is largely demilitarized. But Israel has regularly agreed to Egypt bringing in reinforcements to tackle the Sinai insurgency, and one Israeli official signalled there could be further such deployments following the new attacks.

"This incident is a game-changer," the official said. "We are attentive to Egypt's needs, as always."

President Sisi said he would bring in tougher legal measures in coming days after the killing of the prosecutor, Hisham Barakat, the most senior Egyptian official to die in such an attack in years.

Mr Sisi's government does not distinguish between the now-outlawed Brotherhood - which says it is committed to peaceful activism - and other militants.