GAZA CITY ø Hamas said it has been developing a long-range Kassam-class missile.

Hamas sources said the Islamic insurgency group has been working on a so-called Kassam-4 missile. The missile was meant to have a range of 17 kilometers and capable of striking the Israeli city of Ashkelon from the northern Gaza Strip.

In 2003, Kassam missiles fired from the edge of the Gaza Strip landed in the industrial zone in southern Ashkelon. Those missiles were said to have traveled around 10 kilometers.

Hamas, believed to have up to 200 Kassams in the Gaza Strip, has claimed a capability of developing missiles to a range of 17-20 kilometers. The group has threatened to begin targeting Ashkelon.

On Monday, Hamas gunners launched at least two Kassam missiles toward the Israeli city of Sderot. During the previous day, Hamas fired two Kassam missiles into Israel's western Negev. There were no serious injuries reported in either strike. Over the last six days, Hamas has fired 13 Kassam missiles into Israel.

For the last six days, Israel's military has conducted a Kassam search-and-destroy operation in the Gaza Strip in which more than 75 Palestinians were killed. The casualties included members of seven Kassam crews. On Monday, seven Palestinians were reported killed in fighting in the northern Gaza Strip.

Israeli military sources said Hamas has been developing Kassam missiles in lathes installed throughout the Gaza Strip. They said Hamas has developed these new missiles with expertise relayed by Hizbullah.

"In the past several years, during the most present conflict, the Palestinians have enhanced their abilities to launch their rockets, which can now reach a range of 10 kilometers, as compared to the three-kilometer-range previously attained," an Israeli military statement said. "Hamas is now trying to develop the Kassam-4 rocket, which will have a far greater range than what exists today."

The military statement described the Kassam as a large iron cylinder body tipped with a small warhead. The missile contains an ejecting nozzle and four small stabilizing wings. The middle part of the rocket comprises the engine, while the front part is the warhead attached to a detonating fuse that contains standard or improvised explosives.

The Kassam-1 has a weight of 5.5 kilograms with a warhead of 0.5 kilograms and a maximim range of three kilometers, the statement said. The Kassam-2, twice as wide and six times heavier, has a range of eight kilometers and a warhead of between five and seven kilograms. The Kassam-3 has a range of 10 kilometers with up to 20 kilograms of explosives. Its diameter is 170 millimeters.

Israeli officials said they don't have the technology to defend against Kassam missiles. They said the Mobile Tactical High Energy Laser project undertaken with the U.S. Army has been hampered by technical obstacles and did not envision an operational system before the end of the decade.

Palestinian sources said Hamas and other insurgency groups have tried to defeat Israeli reconnaissance systems during the military operation in the Gaza Strip. The sources told the London-based Al Hayat daily on Monday that the insurgents were creating smoke screens and other means to conceal their activities from Israeli unmanned aerial vehicles.