Egypt's army said one solider and 19 militants were killed in the third day of its recent air and ground operation against insurgents in in the restive North Sinai region.

Military air forces pounded 31 militant hideouts and arm caches while ground and special troops raided a number of other targets, killing 19 militants, military spokesman Brigadier General Mohamed Samir said in a statement late on Monday.

One soldier was killed during the attacks at Monday dawn, he added.

The military has launched fresh raids against Islamist militants in the region after a Friday attack on an army checkpoint in the Bir Al-Abd area west of El-Arish, the capital of North Sinai, killed 12 soldiers and wounded at least six others. The attack was claimed by Ansar Beit Al-Maqdis .

The army said it killed 33 other militant fighters in response during air and ground raids on Saturday and Sunday.

Egyptian forces have in recent years been battling an Islamist insurgency based in parts of the northern Sinai region, which has mainly targeted police and troops.

Egyptian President Abdel-Fattah El-Sisi said in an interview with three public newspapers published on Saturday that his country's war against Islamic militants in the Sinai Peninsula would be long, but that conditions in the mountainous, thinly populated region were improving.

"The terrorists are evolving and we are improving our operations," he said.