The number of casualties in the Gaza Strip is rising following the resumption of Israel's military offensive against Hamas after a seven-day pause in fighting. Aid groups fear the humanitarian situation will deteriorate as essential supplies are suspended.

The Israeli military announced on Friday morning, after the pause had expired, that it had struck over 200 targets across Gaza, including Rafah and Khan Younis in the south.

Health authorities in Gaza said 178 people had died and 589 people were injured since the fighting resumed.

Hamas's armed wing, Al-Qassam Brigades, posted on social media that it fired rockets toward the Israeli town of Sderot and other areas near the border with Gaza in retaliation against Israeli attacks on civilians.

The Palestine Red Crescent Society said in a social media post on Friday that Israeli forces were preventing the entry of aid through the Rafah border crossing. It said Israeli forces informed all organizations and entities operating there that the entry of aid trucks from Egypt to Gaza is prohibited from Friday until further notice.

The society has called for aid supplies to be allowed into the enclave as soon as possible, as halting the deliveries will only add to the suffering of civilians.

UN humanitarian chief Martin Griffiths said in a statement on Friday that people in Gaza "have nowhere safe to go and very little to survive on. They live surrounded by disease, destruction and death."

Griffiths is the Under-Secretary-General for Humanitarian Affairs and Emergency Relief Coordinator. He called for a ceasefire and said, "We need to maintain -- and build on -- the progress in aid delivery."