The Israeli navy says it thwarted a marine attack on Monday when it opened fire on a boat off the Gaza Strip, killing four Palestinians in wetsuits.

Hamas police officers patrol the beach in front of the city of Gaza after the Israeli navy killed four men in diving suits before dawn on Monday. (Lefteris Pitarakis/Associated Press)

Israel's army said the boat was discovered carrying a squad of armed men wearing wetsuits early Monday morning. The army said it believed the men were setting out to carry out an attack.

In a message sent to media in the Gaza Strip, the Al-Aqsa Martyrs Brigade said the four dead were part of its marine unit. The militant group, which has ties to the Fatah party headed by Palestinian Authority President Mahmoud Abbas, said the marine unit was conducting training in Gaza's waters.

Moawiya Hassanain, a Palestinian health official, said the four bodies were taken to a hospital in central Gaza.

The Israeli unit responsible for intercepting the boat is the same naval commando group involved in a May 31 raid on a flotilla of aid that attempted to break the Israeli blockade against the Gaza Strip, which is controlled by Hamas.

Army officials said Monday's interception is a shot in the arm for a unit that has been under scrutiny since the storming of the flotilla left nine dead and several injured. The dead included eight Turks and one Turkish-American.

The flotilla raid renewed international attention on the three-year-old blockade against Gaza, which Israel says is necessary to isolate Hamas militants and keep them from expanding their arsenals.

The incident also prompted calls for an international investigation, but Israel has rejected the idea. Israel has said it has the right to conduct its own investigation, perhaps with limited foreign observation.

On Monday, Turkish Foreign Minsiter Ahmet Davutoglu said Israel should agree to the probe proposed by United Nations Secretary General Ban Ki-moon. Davutoglu said: "Otherwise, it means that they have something to hide."

"The international community is facing a serious test. Does a country have the right to intercept a ship in international waters or not?" Davutoglu said.

The flotilla raid has strained relations between Israel and Turkey. The Turks have said they will reduce military and trade ties with Israel, and they've threatened to break relations unless Israel apologizes for the action.

With files from The Associated Press