One member of the Islamic Jihad group was killed and another injured after an Israeli air strike hit their vehicle as it was travelling close to the Jabaliya refugee camp.
A member of the armed wing of the ruling Palestinian movement Hamas was shot and killed in Beit Hanoun earlier on Sunday.
A member of the security forces close to Fatah was killed in nearby Beit Lahiya, medics said.
Israeli forces have killed 48 people since its Operation Autumn Clouds began on Wednesday, more than half of them gunmen, according to Palestinian medical officials.
A four-year-old, a 12-year-old, two teenagers and a 70-year-old have also been among the victims.
One Israeli soldier has been killed during the operation.
In Beit Hanoun, tanks and bulldozers surrounded the town's hospital. Soldiers said that they would open fire on anyone trying to enter or leave the building, witnesses said.
Nasser Raduane, the deputy director of the hospital, told AFP news agency: "The soldiers in tanks ordered us to close the doors of the hospital and said not to move, otherwise they'll fire."
He said the building did not have electricity or enough water for its patients.
A Palestinian resistance group, meanwhile, has said that the offensive can endanger the life of a captured Israeli soldier.
Abu Mujahid, a spokesman for the Popular Resistance Committees (PRC), said: "We have no intention of killing the prisoner Gilad Shalit, but the Israeli air raids are risking killing him. The soldier is alive."
The PRC was one of three groups which claimed responsibility for the June 25 cross-border raid in which Shalit was captured and two other Israeli soldiers killed.
Mujahid said he was speaking on behalf of all three groups, which also include the armed wing of Hamas and Islamic Jihad.
The Israeli government has said that Operation Autumn Clouds was carried out to stop rockets being fired into Israel.
Ehud Olmert, the Israeli prime minister, said: "We have declared that we will never accept the ongoing Qassam [rocket] fire and that we would take any steps needed to considerably reduce the fire and prevent terror activity.
"We have said so, we are doing so and we will continue to do so. The operation is limited in time but we have no intention of announcing when it will end."
At least one homemade missile hit the Israeli border town of Sderot on Sunday, the Zaka rescue service said. No one was hurt.