Pope Benedict XVI, meanwhile, appealed "to stop the blood flowing" in the impoverished Palestinian territory.
Amid the rising death toll, Gaza fighters warned that the operation was risking the life of an Israeli soldier they seized in late June, though they said they did not intend to kill the serviceman.
A member of the armed wing of the ruling Palestinian movement Hamas was shot dead in Beit Hanun and a member of the security forces close to president Mahmud Abbas's Fatah party was killed in nearby Beit Lahiya, medics said.
In Beit Hanun, which Israel says has become a launchpad for rocket fire and which has borne the brunt of its "Operation Autumn Clouds" launched Wednesday, tanks and bulldozers surrounded the northern town's hospital.
Soldiers warned through loudspeakers that they would open fire on anyone trying to enter or leave the building, witnesses said.
"The soldiers in tanks ordered us to close the doors of the hospital and said not to move, otherwise they'll fire," deputy hospital director Nasser Raduane told AFP by telephone.
He said the building did not have electricity or enough water for its patients.
The army said that it was not aware of the warnings. "There is only one tank in position near the hospital, but there is nothing extraordinary going on ... We're not aware of such warnings," a spokesman said.
At the Vatican, Pope Benedict voiced concern over the deteriorating situation in the beleaguered coastal strip and expressed "my support for the civilian population who suffer the consequences of these acts of violence".
He asked pilgrims gathered in Saint Peter's Square to pray "that our almighty and merciful God enlighten the Israeli and Palestinian authorities and all the countries working in the region to find a way to stop the blood flowing".
The current Israeli operation is the largest since Corporal Gilad Shalit was seized in a cross-border raid on June 25, which killed two other soldiers and sparked a massive Israeli offensive in Gaza.
The groups which claimed responsibility for the raid warned on Sunday that the Israeli operations were endangering the serviceman's life.
"We have no intention of killing the prisoner Gilad Shalit, but the Israeli air raids are risking killing him," said Abu Mujahid, a spokesman for the Popular Resistance Committees.
Israeli Prime Minister Ehud Olmert said the operation would continue for as long as necessary, but that the Jewish state had no intention of reoccupying the Gaza Strip from which it withdrew last year.
"We have declared that we will never accept the ongoing Qassam fire and that we would take any steps needed to considerably reduce the fire and prevent terror activity," he said, referring to the home-made rockets fired at Israeli territory by Gaza-based militants.
"When we reach the conclusion that the effectiveness of the operation is bringing us closer to reaching our goals, we will definitely pull our forces out of Gaza. We have no intention to conquer Gaza, we have no intention to stay in Gaza."
The five-day blitz on Gaza has failed to stem the rockets, however, with four projectiles falling on southern Israel on Sunday and 34 in all since early Wednesday, according to the army, lightly injuring three people.
Rockets fired from Gaza have been an almost constant curse in communities bordering Gaza since Israel left the territory in 2005 and closed the curtain on a 38-year occupation.
In all, Operation Autumn Clouds has killed 47 Palestinians and one Israeli soldier. Among the victims have been a four-year-old, a 12-year-old, two teenagers, a 70-year-old and at least 25 militants.
More than 200 people have been wounded, according to rescue services.

Copyright AFP (Agence France-Presse), 2006