Defence Minister Abdel-Fattah El-Sisi on Tuesday said in a speech before the military academy graduates that Egypt was currently facing "enormous challenges" on the economic, political and social fronts that have the potential to threaten Egypt's national security.

Failure to resolve the current political crisis would have "serious implications for the country's stability," El-Sisi added, according to the official Facebook page of a spokesman for Egypt's Supreme Military Council.

On Tuesday night, numerous Suez Canal residents demonstrated in the streets in defiance of a curfew imposed by President Mohamed Morsi. Meanwhile, 22 people were injured in ongoing clashes with police in Port Said.

El-Sisi stated that the armed forces were in a "difficult situation" in which they had to balance Egyptians' right to stage peaceful protests with a mandate to protect vital institutions of state.

On Sunday night, Morsi imposed a 30-day state of emergency in the Suez, Ismailia and Port Said governorates. He also introduced legislation granting Egypt's armed forces the authority to "safeguard state institutions against saboteurs and restore security."

Early Saturday, military forces deployed in Suez after seven protesters and a soldier were shot dead in Friday clashes on the second anniversary of Egypt's Tahrir Square uprising.

The death toll rose dramatically in Port Said on Saturday when a court sentenced 21 Port Said residents to death for involvement in last February's Port Said stadium disaster, in which scores of football fans were killed. Since then, the city has witnessed intense rioting, with residents accusing the central government of marginalising them.

Clashes between security forces and anti-government protesters have continued intermittently across the country, with at least 52 people reported killed nationwide.

President Morsi appointed El-Sisi defence minister last summer after sending his predecessor – Hussein Tantawi, former head of the Supreme Military Council – into mandatory retirement.