At least 40 people were killed and some others injured on Sunday evening in Israeli bombing of tents in northwestern Rafah, the southernmost city in the Gaza Strip, the Palestinian official news agency WAFA reported.

Israeli forces fired about eight rockets toward the tents in a newly established camp crowded with thousands of displaced people near the warehouses of the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA), WAFA added.

Local sources told Xinhua that it was a "severe and unprecedented" Israeli air strike on the densely populated area of displaced families, igniting tents made of plastic and tin, as well as civilian vehicles.

Video clips circulated on Facebook showed flames rising intensively in the area and fires engulfing tents still inhabited by many, including children and women.

The sources said the civil defense and ambulance crews face significant obstacles in retrieving the bodies due to the difficult terrain.

Palestinian security sources told Xinhua that crowded with Gazans, the area had been classified by the Israeli military as a "safe area" before the strike.

In a statement released on Sunday night, Hamas slammed the bombing as "complete defiance and disregard for the decision of the International Court of Justice (ICJ) that demanded it to stop its aggression against Rafah."

It also said Israel would not have acted without U.S. support and approval, adding that it held the U.S. administration fully responsible for the deadly attack.

The Israel Defense Forces (IDF) said in a statement that "an IDF aircraft struck a Hamas compound in Rafah in which significant Hamas terrorists were operating."

"The strike was carried out against legitimate targets under international law, using precise munitions and on the basis of precise intelligence that indicated Hamas' use of the area," it added.

The Israeli air strike came hours after Al-Qassam Brigades, the Hamas armed wing, launched a large rocket barrage from Rafah towards the coastal city of Tel Aviv in central Israel for the first time in months.

On May 7, the Israeli army announced that it had taken control of the Palestinian side of the Rafah crossing, situated south of the Gaza Strip on the border with Egypt and in the eastern area of Rafah, which resulted in a halt to aid entering Gaza.

Israel considers Rafah a last stronghold for Hamas, which has controlled the Gaza Strip since 2007.