Six members of Hamas were killed in an explosion in the central Gaza Strip on Saturday, which the military wing of Hamas has blamed on Israel.
While Israel declined to comment on the explosion, it did confirm another strike on Sunday, which it said as was a reaction to kite-borne fire bombings.
Gaza's health ministry confirmed six people were killed on Saturday's explosion, with three others wounded in what residents said appeared to be an accidental explosion in the Zawayda area of the central Gaza Strip.
The health ministry said the explosion may have been caused by the handling of explosives. In the past some explosions in the Gaza Strip have resulted from the accidental detonation of explosive materials belonging to militant groups.
However a statement from the Palestinian Islamist group's armed wing insisted that the incident was a "deplorable Zionist crime".
The Ezzedine Al Qassam Brigades, the armed wing of Gaza's rulers, said the fatalities were members of their group and blamed Israel for the explosion but did not provide details or proof.
The incident occurred during a "complex security and intelligence operation", the group said in a statement, calling it "serious and large security incident" and blaming the "Zionist enemy".
The statement added that it was a "serious crime against our fighters".
Reuters television showed smoke rising above the village of Zawayda, far from the border with Israel where tensions have escalated in recent weeks.
An Israeli military spokesman declined to comment on the incident, although a more junior official had earlier denied the army was involved. Israel and the West designate Hamas as a terrorist organisation.
In a separate incident, Israel struck a facility belonging to Hamas' military wing overnight, with the Israeli military on Sunday saying it was responding to kite-borne fire bombings.
A new tactic has seen some Palestinians flying kites with incendiary devices attached across the Gaza border into Israel in an attempt to set farmers' fields alight.
"Last night an aircraft struck a terror post belonging to the Hamas terror organisation adjacent to the security fence in the northern Gaza Strip," a spokeswoman told AFP, without describing the target.
Hamas's Ezzedine al-Qassam Brigades military wing said in a statement that it was a border observation post and that nobody was injured in the attack.
"The strike was in response to an incident that took place yesterday in which terrorists launched burning incendiaries in an attempt to light fires in Israeli territory," the Israeli spokeswoman said.
Israeli media have in recent days reported significant damage to farms due to kite-flown Molotov cocktails, though the devices face difficult odds in making it across the fence while staying alight.
The tit-for-tat attacks follow weeks of deadly protests and clashes along the border between Gaza.
At least 41 Palestinians have been killed since protests broke out on March 30, and thousands more have been injured. Israel claims the marches are being orchestrated by Hamas in an effort to provoke an Israeli response, thus justifying further attacks.