Six soldiers were killed in an attack. (AP Photo/Ravy Shaker)

Six Egyptian soldiers have been killed in an attack by suspected extremists on a security checkpoint in volatile northern Sinai, the army said on Friday.

The "terrorist elements" used hand grenades and firearms in the attack in al-Arish, the capital city of northern Sinai, the army said in a statement on its official Facebook page.

An ensuing clash erupted between the attackers and the troops, resulting in unspecified casualties among the assailants, the statement said.

"The area is being combed in pursuit of the fugitive terrorist elements."

The statement did not say exactly when the attack had been carried out, but witnesses said it took place Thursday evening.

There has been no claim of responsibility.

Egypt has seen a series of deadly attacks, mainly targeting security forces and the country's Christian minority, since the army's overthrow in 2013 of Islamist president Mohammed Morsi following mass protests against his rule.

Most of the attacks were claimed by an affiliate of the Islamic State radical militia.