Israel Air Force jets struck two smuggling tunnels in the southern Gaza Strip overnight Saturday, just hours after a Qassam rocket fired from the coastal enclave hit a public structure in the western Negev, causing damage.

Open gallery view Qassam rocket fired by Hamas militants. Credit: Getty Images

An Israel Defense Forces spokesperson said the army views Gaza's Hamas rulers as the sole party responsible for the rocket attacks against Israel.

The 36-hour tit-for-tat began Friday, when a rocket fired by Gaza militants exploded in the coastal Israeli city of Ashkelon.

The IAF struck three targets in Gaza Friday night, which Palestinian sources described as the heaviest assault since Operation Cast Lead, Israel's three-week assault on the Gaza Strip a year and a half ago.

A Hamas operative, a 40-year-old member of Hamas' military wing, was killed in an explosion near the Nuseirat refugee camp south of Gaza City in the center of the Hamas-controlled strip. Another 13 Palestinians were hurt.

Hamas has vowed revenge for the militant leader's death.

Palestinian militants then fired a Qassam rocket Saturday night, which hit the Sha'ar Hanegev regional council area in the Negev, just hours after the first IAF strike on Gaza.

According to the IDF spokesperson's office, the rocket damaged the structure's rooftop and destroyed most of the second floor of the building, which serves during the day as a daycare center for people with disabilities.

No injuries were reported in the attack.

IDF patrol units have been scanning the area for the rocket's remains.