The IDF says today (Friday) that the latest significant attack on Hamas' underground system of tunnels has significantly affected the organization's ability to conduct hostilities and that Hamas did not expect this magnitude of violence.

The IDF says it hit Hamas underground headquarters, which was one of Hamas' biggest secrets.

"We hit five of their installations, dramatically affecting their operational capability, including senior officials who were inside and were injured." The IDF adds that Hamas has been building their underground for years and that the organization was confident that it was safe there. "All operations - rocket fire, maneuvers, shootings - came from that underground installation.”

"Hamas has been hit hard; we have dealt critical damage to its team of engineers and scientists. These individuals are irreplaceable," the IDF added.

The IDF Intelligence Division warned that Jerusalem would come under fire during the Jerusalem Day celebrations, and advised canceling the parades and other events.