Israeli troops have entered Gaza at the start of a ground operation to halt rocket fire targeting its citizens.

The first such operation in the territory in just over five years came after Hamas rejected an Egypt-led ceasefire proposal.

The military has tonight called up an additional 18,000 reservists and said the operation would target underground tunnels used for weapons smuggling. It’s understood however that military chiefs may get the go light to extend the mission should it be needed.

“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 Brigadier General 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”.

Thousands of soldiers backed by tanks and huge DC9 bulldozers entered the Hamas-ruled territory after nightfall, security officials and Israeli media said.

Hamas spokesman Fawzi Barhoum said Israel “will pay dearly” for the assault. “Hamas is ready for a confrontation,” he said.

A Gaza security official 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,” he said. “There is also fire from the sea toward police checkpoints.”

The ground operation followed a brief humanitarian truce earlier in which Israel held fire to allow Gazans to stock up on food and other necessities after being largely holed up at home since the conflict began last month.

During the dday, 13 Hamas members tried to infiltrate Israel through a tunnel under the Gaza-Israel border, but were stopped by an Israeli strike at the mouth of the tunnel.

The IDF launched Operation Protective Edge 10 days ago following an upsurge in rocket fire from Gaza. Since then, more than 220 Palestinians including civilians have been killed in the anti-terror mission while one Israeli has also died amid a brrage of 1500 missiles fired towards Israel’s south and centre.

Despite hopes that rocket fire would be stopped through air raids, thousands of Israeli soldiers had massed on the border with Gaza in recent days. Israel had called up 48,000 reserve soldiers.