JERUSALEM, Dec. 23 - Frustrated by continuing rocket fire from Gaza, the territory Israel evacuated over the summer, Israel is trying to enforce a buffer zone in northern Gaza through air and artillery strikes, a deputy defense minister, Zeev Boim, said Friday.

The intention is to prevent Palestinian militants from using former northern Gaza settlements like Dugit and Nissanit, now piles of rubble, to fire rockets into Israel. In the last few days, rockets have hit the outskirts of Ashkelon, raising concerns about a big power plant there, and in Sederot, a regular target of rocket fire. On Thursday, a rocket landed in an Israeli Army base on the border, slightly wounding five soldiers, and Israeli shelling in response killed a Palestinian in Jabaliya.

Israel, in the midst of an election campaign, is threatening a temporary reinvasion of northern Gaza with ground troops, though the preference is to discourage the rocket firing through shelling and airstrikes - mostly on open fields where rockets are sometimes fired.

But Mr. Boim on Friday suggested that Israel might fire artillery toward populated areas as well. "We need to tell the residents of Beit Hanoun, Beit Lahiya and the suburbs of Jabaliya: ´In 12 hours, artillery will land in the area; evacuate these areas,´ " he told Israeli Army radio. "I think one operation of this sort can solve the problem."

Palestinian security forces who are patrolling northern Gaza and say they are trying to stop the rocket fire also say they will not evacuate the area, which they now consider sovereign and liberated Palestinian land.

So Israelis are imagining other ways to create popular pressure on the militants to stop firing, with suggestions that Israel cut off all electrical power to Gaza, a move of dubious legality. Human Rights Watch, for instance, says that such a cutoff would constitute collective punishment of a civilian population under international law.

On Friday, Yuval Steinitz, the Likud Party chairman of Parliament´s foreign affairs and defense committee, said he could not rule out an electricity cut. "It can´t be that they fire at us from there and we provide electricity," he said, suggesting an hour cut for each rocket fired, and a whole day if there are casualties.

Senior army officials oppose the electricity cuts. But they supported an earlier pressure tactic: Israeli fighter planes flew regularly over Gaza in the middle of the night, creating sonic booms to keep the population awake and jittery.

Prime Minister Ariel Sharon pulled out of Gaza, arguing that Israel would then be freer to use its air power and artillery once the Israeli settlers and army were gone. His rivals, like Benjamin Netanyahu, who quit the cabinet and now leads the Likud Party that Mr. Sharon abandoned, argued that the pullout would damage Israeli security, while doing little to stop rocket fire.

For a time, the rocket fire lessened, but it increased after an Israeli decision to resume targeted killings of militants in Gaza. The militants say they are only responding to Israeli violations of a so-called cease-fire, while Israel says it is attacking the heads of organizations responsible for attacks like the Dec. 5 suicide bombing in Netanya.

Israel is also reluctant to make the political life of the Palestinian president, Mahmoud Abbas, even more difficult than it already is. Israel is trying to maneuver him into canceling Palestinian parliamentary elections on Jan. 25, fearing a strong showing by the militant Hamas group, which is sworn to Israel´s destruction.

Mr. Abbas is trying to patch together a single slate of candidates for his main Fatah faction in the face of a challenge from a younger group led by the imprisoned Marwan Barghouti. On Friday, the Palestinian prime minister, Ahmed Qurei, said he would not run for the legislature and told Mr. Abbas that he favored postponing the elections and opposed a joint slate.

Thousands of Hamas supporters marched in a rainy Gaza on Friday to demand that Mr. Abbas keep to his vow to hold the elections.

As for Mr. Sharon, who suffered a mild stroke this week, he is surprisingly healthy for a man of his height and weight - at least according to medical records somehow leaked to Israel´s most popular daily, Yediot Aharonot. Mr. Sharon, 77, who is just under 5 feet 7 inches tall and weighs 313 pounds, nonetheless has a blood pressure of 120 over 80 and a cholesterol level of 195, which his doctor says are within normal range.