The Hamas militant group said it remains committed to a cease-fire with Israel, but will not act as Israel's police force" in confronting militants who breech the truce.

The comments by Hamas leader Khalil al-Haya came shortly after Gaza militants fired three rockets into southern Israel Tuesday, lightly wounding two Israelis. It was the first attack since the truce took effect last Thursday.

Israel responded by closing Gaza's border crossings, which are used to deliver food and basic supplies into the area.

Hamas said it was exerting pressure on Islamic Jihad, which claimed responsibility for the attack, to stop the rocket fire and demanded that Israel open the crossings. But al-Haya said its forces would not confront rocket launching squads on the ground.

Even if there is a violation by some factions, Hamas emphasizes its commitment to the calm and is working to implement the calm," al-Haya said.

But Hamas is not going to be a police securing the border of the occupation," he added. No one will enjoy a happy moment seeing Hamas holding a rifle in the face of a resistance fighter."

Israel called the rocket attack a gross violation" of the Egypt-mediated truce. As part of the cease-fire, Israel had on Sunday begun incrementally increasing the amount of goods entering Gaza. On Wednesday, all cargo crossings were closed, though a pedestrian passage was kept open.

Hamas spokesman Taher Nunu said the closure was a clear violation of the calm" and called on Egypt, which mediated the truce, to intervene. We will not accept leaving our people hostages to this policy," he said.

Islamic Jihad said the rocket attack was a response to an Israeli raid on the West Bank that killed an Islamic Jihad commander. The West Bank is not included in the truce. Islamic Jihad and other Gaza factions reluctantly agreed to the truce but were angered that the deal didn't include an Israeli cessation of West Bank operations.

Gaza and the West Bank are separate geographical entities located on opposite sides of Israel.

Islamic Jihad had said Tuesday after a meeting with Hamas that the rockets were an exceptional" response to the West Bank fighting, suggesting that they would abstain from further rocket fire.

Many previous Israeli-Palestinian truces have unraveled in such ways, with minor violence gradually escalating and spiraling out of control. The sides committed to the truce for six months.

But both sides were eager to keep the fragile deal intact, with Hamas wanting to solidify its hold over the territory it overran last year by reopening the crossings and Israel hoping to bring quiet to southern areas where life has been paralyzed by the falling projectiles.

In violence Wednesday, an elderly man was shot along Gaza's border with Israel and moderately wounded, Palestinian doctors said.

The man, 81, was walking east of Khan Younis in southern Gaza when he was shot in the arm and hand. His family and Hamas accused Israel of shooting the man. The Israeli army said it didn't know of any such incident.