Three Palestinians were killed by an Israeli shell on Thursday near a rocket launcher in northern Gaza shortly after two make-shift rockets were fired into Israel, damaging a water pipe and a building.
Palestinian residents and witnesses said the three were teenage shepherds.
An Israeli military spokesman said the three had been tampering with a rocket launcher when they were fired on.
Earlier, Israeli special forces backed by a transport helicopter killed a woman in a raid on a house in the southern Gaza Strip.
The woman, 35, died after soldiers stormed the house belonging to a member of the governing Hamas movement near Rafah, a town on Gaza's southern border with Egypt.
The troops also wounded a boy in the house, and two other Palestinians, and arrested one man.
Israeli troops also killed a man, 24, in a separate incident in Rafah. An Israeli military source said that troops had returned fire after gunmen shot at them from a house.
Israeli soldiers swept into the town under darkness in lightly armoured Jeeps, and a transport helicopter landed at the site after clashes erupted, possibly to evacuate casualties, witnesses said.
Rafah is an area where Israel believes a soldier, Corporal Gilad Shalit, captured by Gaza fighters in a June 25 border raid might be held.
The operation followed an increase in rocket attacks from Gaza on southern Israel.
Israeli radio reported that at least one rocket had been fired early on Thursday, causing no casualties.
An Israeli military spokesman confirmed that troops were raiding the Rafah area, but had no further comment.
Israeli forces have mounted several major operations in Gaza since Shalit's capture, killing more than 210 Palestinians, about half of them civilians.