Hamas said it fired rockets at Israeli commercial hub Tel Aviv on Thursday in its first military response to the growing civilian death toll from Israel's resumption of air and ground operations in Gaza.

Israel said it had closed off the territory's main north-south route as troops expanded the ground operations they resumed on Wednesday.

Gaza's civil defence agency said 504 people had been killed so far in the Israeli assault this week, including more than 190 children.

The armed wing of Hamas, the Ezzedine al-Qassam Brigades, said it fired rockets at Tel Aviv in response to Israel's "massacres" of Gaza civilians.

The Israeli army said it intercepted one projectile fired from Gaza and that two others struck an uninhabited area.

After weeks of stalemate, Israel resumed its air campaign early on Tuesday with a wave of deadly strikes that drew widespread condemnation.

The offensive shattered a relative calm that had pervaded the war-ravaged Palestinian territory since a ceasefire took hold on January 19.

US President Donald Trump "fully supports" Israel's deadly resumption of air and ground operations in Gaza, White House Press Secretary Karoline Leavitt told reporters on Thursday when asked if he was trying to get a Gaza ceasefire back on track. (AFP)