Cairo - Militants exchanged shots with an Egyptian coastguard vessel in the Mediterranean Sea on Thursday, causing it to catch fire, the military said in a statement.
There was no immediate claim of responsibility for the attack on the coast of northern Sinai, an area bordering Israel and the Gaza Strip.
Such incidents at sea are rare, though Egypt is battling an Islamist insurgency in the region. On July 1, 100 militants and at least 17 members of the security forces were killed in a single day of clashes.
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"The [coastguard] launch crew suspected the movements of some terrorist elements on the coast, so it chased [them] and exchanged gunfire, which led to the launch catching fire without loss of life," said the statement posted to Facebook.
Military sources said the suspected militants had fled after firing on the vessel.
A Reuters witness in Gaza saw a plume of dark grey smoke rising from a boat off the coast. Other witnesses in the Palestinian enclave said they heard explosions and gunfire.
An Israeli military spokesperson said Israel was not involved in the incident and had not been asked to assist.
In November, four assailants were killed and 32 people detained when gunmen in a fishing boat opened fired on an Egyptian naval launch north of Damietta port, near the Suez Canal and west of Thursday's incident.