Jerusalem: Describing the ground offensive in Gaza as “unavoidable”, Israel on Sunday pledged to extend and intensify the operation amid heavy exchange of fire between troops and the Hamas militants that have taken the death toll in the coastal territory beyond 500.

Palestinian sources in Gaza said that 23 Palestinians have been killed in the Israeli offensive, three of them top Hamas militants, as Israeli troops targeted traffic routes bisecting the Hamas ruled territory in two parts.

Shells fired by Israel Defence Forces (IDF) troops exploded in the centre of Gaza City’s main shopping area, leaving five dead and dozens wounded, the sources said.

An Israeli reconnaissance plane fired a missile at the home of Democratic Front for the Liberation of Palestine, Muhammad Abid Barbakh, killing him and four others, Palestinian news agency, Ma’an, reported.

They were identified Barbakh’s father, Abid, his two brothers Mahdi and Yousif and his nephew Mousa.

Thirty IDF soldiers were also wounded in the clashes, two of them seriously.

Black smoke billowed all across the Strip as Israeli tanks and troops from elite brigades marched into the Hamas ruled territory on Saturday evening, following bomb-sniffing dogs to ensure that their routes had not been booby-trapped.

Defence minister Ehud Barak told the cabinet that while the operation was bound to be difficult, it “will be extended and intensified as necessary.”

“War is full of surprises and difficult challenges but our best fighters are leading the operation,” Barak said.