Israeli jets struck Hamas military training sites in Gaza early Thursday in response to rocket fire against Israel a day earlier.
No casualties are reported on either side.
A radical Islamist Salafist group that backs Islamic State claimed responsibility for Wednesday's rocket attack. It said it was out to avenge the killing of one of its members by Hamas.
"We are continuing with our jihad against the Jews, the enemies of God and no one will be able to deter us," the group said in a statement, using the term in Arabic for holy war.
Hamas rules Gaza and Israel considers the group responsible for all activities there.
A nearly two-month long war between Israel and Hamas last year killed more than 2000 Palestinian civilians and obliterated entire neighborhoods.
