An Israeli rocket is fired into the northern Gaza Strip July 17, 2014. Israeli Prime Minister Benjamin Netanyahu on Thursday instructed the military to begin a ground offensive in Gaza, an official statement from his office said.  [Photo/Agencies]

GAZA CITY, Gaza Strip - Thousands of Israeli soldiers backed by tanks invaded the Gaza Strip on Thursday, a military spokesman said, escalating a 10-day military operation to try to destroy Hamas' weapons arsenal, rocket firing abilities and tunnels used to send militants from the Palestinian territory into Israel.

In photos: Gaza weeps in war

Cease-fire between Hamas, Israel starts in Gaza

The high-stakes move was compelled by Israel's growing exasperation over unrelenting rocket fire and followed the collapse of Egyptian-led efforts to broker a cease-fire. It also came after a failed attempt by 13 militants to infiltrate Israel earlier Thursday through a tunnel under the Gaza-Israel border, only to be stopped by an Israeli strike at the mouth of the tunnel.

The military said the first major Israeli ground offensive in Gaza in just over five years was open-ended and would be carried out on several fronts in the coastal strip.

"Our forces, large ground forces accompanied by massive air force support, naval forces and intelligence, are taking over targets in Gaza, operating against tunnels and terror activists and infrastructure," Israel's chief military spokesman Brig. Gen. Motti Almoz said.

He called on Gaza residents to evacuate areas where the military is operating, warning the "military is operating there with very great force."

Hamas spokesman Fawzi Barhoum said Israel ``will pay dearly'' for the assault. "Hamas is ready for a confrontation," he said.

An official in the Gaza security operations room reported heavy Israeli tank shelling along Gaza's border areas with Israel since 8 p.m. Thursday.

"All border areas are under fire. There is a tank shell every minute," said the official, speaking on condition of anonymity in line with briefing regulations. ``There is also fire from the sea toward police checkpoints."

Residents said the northern Gaza town of Beit Lahiya came under heavy Israeli shelling. "There is the sound of tank shells all the time," said Jamal Abu Samra, 42, a farmer in the area. He said his wife, six children, four brothers and their families were huddling on the ground floor of the family home.

"We don't have power since the afternoon so we are listing to the (battery-operated) radio to hear the news," he said.