CAIRO (AP) — An Egyptian navy vessel caught fire off the coast of Sinai on Thursday after an exchange of gunshots with militants from the shore, the military said.

There were no fatalities among the vessel's crew in the shootout with "terrorists," according to a statement by the military spokesman, Brig. Gen. Mohammed Samir, posted on his Facebook page.

Samir did not say how much damage the vessel suffered and gave no details on the type of ship or the size of its crew. However, security officials said an unspecified number of crew members suffered injuries from the fire.

A witness, fisherman Abu Ibrahim Mohammed from the neighboring Gaza Strip, said the vessel was a gunboat that was about a nautical mile off the coast when it caught fire. He did not hear the explosion but saw two smaller boats later trying to put out the fire and that a third, larger one later arrived and towed the burned vessel away. Two speed boats were seen later combing the area as gunshots occasionally rang out, he added.

The vessel, according to the security officials, routinely patrols Egyptian territorial waters and has frequently been used to transport army and police personnel to mainland Egypt, the officials said. The sea route avoids the overland journey through Sinai, where Islamic militants target government forces.

Authorities were also looking into the possibility that the vessel was first hit by a rocket from the shore or that suspected militants swam out to it and placed explosives, which were later detonated by remote control, said the officials, who spoke on condition of anonymity because they were not authorized to speak to the media.

On Wednesday, the military said it foiled an attempted attack on a military post on a highway linking Cairo with the Red Sea coast. The driver of a car that was carrying 500 kilograms (1,100 pounds) of dynamite refused to stop at a checkpoint, drawing fire from the troops, the military said. The car then swerved off the road and the driver was killed, the military said in a statement.

Egypt's Islamic State affiliate said it was behind Wednesday's incident, claiming the car's driver was a suicide bomber who had detonated his explosives, killing several soldiers. The authenticity of the claim could not be independently verified, though it was carried by Twitter accounts affiliated with the group.

The military denied the claim.

Egypt faces threats from multiple insurgent factions, including the IS affiliate in Sinai, which the military says killed at least 17 soldiers in a July 1 assault there. Officials from several branches of Egypt's security forces previously told The Associated Press that that attack killed dozens more. In another attack claimed by the IS group, Egypt's state prosecutor, Hisham Barakat, was assassinated in the Cairo suburb of Heliopolis by a car bomb in late June.

On Thursday, a roadside bomb went off at a busy square also in the Heliopolis district, injuring a traffic policeman, security officials said. The bomb targeted the part of Roxy square where traffic and other policemen routinely gather.

Associated Press writer Fares Akram in Gaza City, Gaza Strip, contributed to this report.