Nine members of Hamas and Islamic Jihad were killed overnight Sunday, according to Palestinian sources, when Israeli jets struck 14 sites in Gaza Strip, after a day of near-constant rocket fire on Israeli towns near the Palestinian enclave. But Israeli officials said seven of the fatalities were Hamas operatives killed when a tunnel collapsed upon them.

The targets hit by Israel were “terror sites and concealed rocket launchers,” the IDF spokesman’s office said, confirming direct hits on the targets.

“At least 25 times today Gaza militants put Israeli lives in direct risk from their rocket attacks,” said IDF spokesman Lt. Col. Peter Lerner. “This reality is unbearable and unacceptable. We will continue to act in order to debilitate and incapacitate the Hamas terror infrastructure striking its warehouses, rocket manufacturing capabilities and those that endanger the wellbeing of the Israelis in the south of the country.”

Seven Hamas members were killed and six wounded in an air force strike, according to a statement released by the terror group. Israeli defense officials, however, said that the men were not killed in an airstrike but were rather crushed when a tunnel collapsed on top of them.

Earlier, two members of Islamic Jihad’s armed wing were reported killed when Israeli planes struck the refugee camp of al Bureij in the central Strip, targeting a rocket launching crew.

The army said in a statement that it prevented a rocket attack “by targeting terrorists.” It said a hit was confirmed.

Hamas threatened to hit back. “This is a serious escalation, and the enemy will pay the price,” Hamas spokesman Sami Abu Zuhri wrote on his Facebook page.

Some 25 rockets were fired at Israel over the course of Sunday, most of which landed in open areas.

One rocket caused a fire and another damaged an agricultural building, the Israeli military said. There were no reports of injuries.

Times of Israel staff contributed to this report.