Cairo: Assailants in boats attacked an Egyptian naval vessel in the Mediterranean on Wednesday, prompting the military to send in air support, state media reported.
The navy boat caught fire during the exchange and three of the assailants` boats were destroyed, the official MENA news agency reported.
It said 20 of the assailants had been arrested while the military conducted search and rescue operations, without elaborating.
A military spokesman declined to comment immediately.
The identity of the assailants was not clear. The attack reportedly took place about 70 kilometres (44 miles) from Egypt`s shore.
The Mediterranean Sea is used by drug traffickers and illegal migrant smugglers who have been intercepted by the Egyptian navy in the past.
The country is also fighting a Islamist militant insurgency that has killed scores of policemen and soldiers since the army overthrew Islamist president Mohamed Morsi last year.
The main militant group, Ansar Beit al-Maqdis, has pledged allegiance to the Islamic State organisation in Iraq and Syria.
Its attacks have focused on troops in the restive Sinai Peninsula.