But the sources said the Hamas missiles launched toward Israel since September were more accurate and powerful than those used in previous attacks. They said the Kassam contained standard explosives that more than doubled the blast.

Hamas spokesman Abu Obeideh said Kassam missiles were striking their targets in Israel. He said the enhanced missiles were being produced in the Gaza Strip.

"These rockets can be launched from anywhere," Abu Obeida said. "We are not using smuggled weapons. We are developing these projectiles, which we are manufacturing locally. They are not imported."

Abu Obeida said Hamas was developing more advanced Kassams, but would not elaborate. He said the forthcoming variants would include technology from the BM-21 Grad rocket and other weapons.

"These will go beyond Sderot," Abu Obeida said. "These will hit the heart of Ashkelon and more towns and cities inside Israel. The Israelis will know its range."

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