DHAKA: The battle between Israel and Gazan militants is growing, as the Israel Defense Forces announced early Sunday that it will expand its ground offensive.

On Saturday, Hamas Islamist fighters infiltrated nearby parts of Israel via underground tunnels and clashed with Israeli troops. The use of the tunnels was the main reason Israel gave for launching its ground operation Thursday night, reports CNN.

The IDF is adding additional troops, having called up tens of thousands of reservists at the start of Operation Protective Edge to prepare for the ground operations.

"In preparation for the mission, the forces have undergone an intensified training and thorough planning period and are prepared and stand ready for the task at hand," said IDF spokesman Lt. Col. Peter Lerner in a statement.

The IDF's goal is to weaken Hamas military capabilities, the statement said.

The clashes demonstrated how Israel's conflict with Hamas has now spilled outside -- and even underneath -- Gaza as the ground war entered a third night Saturday.

As midnight approached, a major battle flared in Shaja'ia east of Gaza City, where the horizon along the border was dominated with flashes, explosions and columns of smoke.

Sixty-two people in Gaza had been killed Saturday, the highest daily death toll so far, according to the Gaza Health Ministry.

An example of infiltration occurred earlier in the day when Hamas militants slipped out of a tunnel from central Gaza and fired at Israeli soldiers, killing two of them, Israel's Channel 10 said.

The Hamas gunmen disguised themselves in uniforms belonging to the Israel Defense Forces, the military said.

One of the Hamas gunmen was killed on Israeli soil, and the rest fled back to Gaza and were killed by a helicopter gunship, Channel 10 said.

BDST: 1117 HRS, JUL 20, 2014