Saad, Israel ? Palestinian militants in the Gaza Strip fired what appeared to be two next-generation rockets into Israel on Sunday, marking a strategic shift in warfare that is likely to heighten fears in Israeli border cities.

The rockets, which may have carried up to 22 pounds of explosives, landed harmlessly and were overshadowed by violence in the Negev Desert city of Beersheba, where gunmen linked to the militant Hamas organization killed two Israelis and wounded four others.

Israeli F-16 jets responded to the deadly attack by firing missiles at several targets in the Gaza Strip, including a base used by Palestinian leader Yasser Arafat’s private security detail.

But the launches may prove significant in a region where tensions are already the highest in decades.

Israeli military sources said Palestinian militants in the West Bank and Gaza Strip now have the Kassam-II rockets in their arsenals, exposing tens of thousands of Israelis to attack.

“If they were to use these rockets to hit a city, that would bring the war to a new phase,” said an Israeli Defense Forces spokesman who spoke on condition of anonymity.

The homemade rockets lack a guidance system and are much less powerful than those used by Iraq during the Gulf War, but they travel three times as far as their first-generation cousins and are “precise enough to hit a metropolitan target,” according to an army statement.

“Israel has warned the Palestinian Authority on more than one occasion that if the Kassam-II is fired into Israeli territory, into Israeli towns, this will be considered a new game with new rules,” Israel Radio’s military correspondent, Alan Ben Ami, told listeners Sunday night.

A senior Israeli security official, speaking on condition of anonymity, said Hamas leaders boast that they can load the rockets with chemical payloads.

Israeli soldiers captured eight of the rockets at a roadblock between Nablus and Jenin in the West Bank last week, signaling that Hamas militants are attempting to distribute them to key border points.

“They can produce a lot. The explosives they need for propulsion are very simple to produce as well,” the senior security official said.

One of the rockets landed near a communal village, or kibbutz, 4 miles from the Gaza border in Saad. Another fell at a nearby cooperative farm, nearly 5 miles from the border.

Hours after the launches, Palestinian officials said their security agents had arrested Adnan al-Ghoul, considered Hamas’ top engineer. They said al-Ghoul helped develop the Kassam rockets.