The blasts in the city of al-Arish came a day after the second round of a parliamentary election closed.
There was no immediate claim of responsibility.
ISIS's Egypt affiliate, Sinai Province, has carried out similar attacks in the region as part of its bid to topple the Cairo government.
State television and security sources first said a car bomb exploded then a second blast hit the area about ten minutes later.
Ambulances rushed to the scene, which was sealed off by soldiers and police, said the security sources.
Egypt's parliamentary Votes count counting process started on Monday evening following the second stage's final day of ballot casting in Egypt's parliamentary elections.
Monday, which saw Public sector employees given a half day off to allow time for voting, marked the last day before run-offs on 1 December and 2 December.