Also on Sunday, Palestinian fighters in the Gaza Strip fired a rocket at Israel in violation of a truce in effect since last week, an Israeli military spokeswoman said.
The rocket caused no injuries or damage.
Under the November 26 truce, Palestinian groups said they would halt rocket fire at Israel if Israel stopped attacks against Palestinians.
Israel ended a five-month offensive in Gaza afterwards but has not halted military patrols and searches for fighters in the West Bank, where the ceasefire is not in effect.
Since the truce took effect, Gaza fighters have launched 16 homemade rockets into Israel, the army has said, causing no casualties and little damage - 11 were within in the first hours of the truce.
Palestinian groups said they would halt rocket fire at Israel if Israel stopped attacks against Palestinians
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Abu Obeideh, a Hamas spokesperson, said: "I wouldn't rule out ending the ceasefire in a few short days if the enemy continues like this."
The Gaza offensive, billed mainly as an attempt to stop daily rocket strikes, was launched after armed Palestinian groups in Gaza, including the governing Hamas faction, captured an Israeli soldier in a cross-border raid in June.
Ehud Olmert, the Israeli prime minister, told the Israeli parliament's Foreign Affairs and Defence Committee on Monday that the government would react with restraint to the continuing attacks, adding that the rocket fire didn't cease during Israel's military operations in Gaza, either.
He said: "It was clear that there would not be an absolute halt to hostilities, but we must remember that until now we haven't found an alternative formula to stop the rocket fire and weapons smuggling.
"We will fully explore every possibility that can lead to momentum to begin a diplomatic process, and so we are now giving the truce a chance."
In an effort to bolster the ceasefire, senior military officials said on Monday that they had decided to reduce their West Bank operations, allowing only regional or division commanders to order arrest raids, instead of the lower-ranking brigade commanders.
The officials spoke on condition of anonymity because they were not authorised to speak to the media.
Palestinian officials called for an end to the raids.
Saeb Erekat, a Palestinian negotiator, said: "We urge [Israel] to stop arrests, incursions, and to give the cease-fire the chance it deserves."