Egypt's naval forces thwarted on Wednesday an attack on one of its boats, according to reports from a military source to Al-Ahram's Arabic website reported.
A naval boat was performing a combat exercise in the Mediterranean, 40 nautical miles north of Damietta's port, when a number of boats fired at it.
Air and naval reinforcement forces were summoned to respond to the attack. A crossfire ensued leading to the destruction of three of the attacking boats.
Twenty of the assailants were arrested.
The army has been combating a decade-long jihadist insurgency in Sinai, with attacks increasing over the past year and expanding into Cairo and the Nile Delta. Hundreds of soldiers and police have been killed, while the army says it has killed and arrested hundreds of jihadists. Civilians have also been caught in the violence.
No information has been released on the identity of the assailants.
This is the first attack on the army's naval forces.