Two Palestinians were killed by an Israeli drone strike on southern Gaza early Monday, medical sources said, just hours after two others were killed in a separate attack.
Gaza Strip health services spokesman Ashraf al-Qudra said two Palestinians were killed and two others wounded in the attack east of Rafah.
Witnesses said the fatalities were militants but those wounded were civilians.
Ezzedine al-Qassam Brigades, Hamas's military wing, said meanwhile that six of their men were killed by the Israeli strike on Rafah.
Qudra did not confirm the Qassam statement. Witnesses said Qassam members were killed when a tunnel had collapsed on them following the Israeli strike.
The Israeli army said it had "targeted nine terror sites and concealed rocket launchers across the Gaza Strip", noting in a statement its attacks came after militants had fired over 25 mortars and rockets at Israel on Sunday.
Late Sunday two other Palestinian militants were killed in an Israeli drone strike east of Bureij refugee camp, near central Gaza's border with the Jewish state, emergency services said.
The Israeli army said it had targeted "terrorists involved in rocket launching".
The strikes come after the brutal murder of 16-year-old Mohammed Abu Khder on July 2 triggered four days of violent clashes that broke out in east Jerusalem and have spread throughout Arab towns in Israel.