Unknown assailants opened fire on a Central Security checkpoint in Arish on Sunday, causing no casualties. 

An eyewitness said that a four-by-four vehicle carrying gunmen targeted the checkpoint from three different directions.

Army forces responded to the attack while aircrafts hovered above the area. 

Twenty-one people have been killed while 122 were wounded in armed attacks in the Sinai Peninsula since the army's ouster of Islamist President Mohamed Mursi on July 3 following mass anti-regime demonstrations.

The victims include seven civilians and army and police personnel.

Since Mursi was ousted, reports of armed attacks in the Sinai Peninsula have increased.