Qatar called on the international community on Wednesday to prevent a "genocide" in Rafah following Israel's seizure of the Gaza city's crossing with Egypt and threats of a wider assault.

In a statement the Gulf state, which has been mediating between Israel and militant group Hamas, appealed "for urgent international action to prevent the city from being invaded and a crime of genocide being committed".

Israel struck targets in the Gaza Strip on Wednesday after seizing the main border crossing with Egypt. Israel has vowed for weeks to launch a ground incursion into Rafah, despite a clamour of international objection.

The attacks on the southern city, which is packed with displaced civilians, came as negotiators and mediators met in Cairo to try to hammer out a hostage-release and truce deal in the seven-month war.

Qatar, which has hosted Hamas's political office in Doha since 2012, has been engaged -- along with Egypt and the United States -- in months of behind-the-scenes mediation between Israel and the Palestinian group.

Israel reopens Kerem Shalom border crossing

Israel said it reopened the Kerem Shalom border crossing to humanitarian aid for Gaza Wednesday, four days after closing it in response to a rocket attack that killed four soldiers.

"Trucks from Egypt carrying humanitarian aid, including food, water, shelter equipment, medicine and medical equipment donated by the international community are already arriving at the crossing," the army said in a joint statement with COGAT, the defence ministry body that oversees Palestinian civil affairs.

The supplies will be transferred to the Gaza side of the crossing after undergoing inspection, it added.

The statement said the Erez border crossing between Israel and northern Gaza is also open for aid deliveries into the Palestinian territory.

The Kerem Shalom crossing was closed after a Hamas rocket attack killed four soldiers and wounded more than a dozen on Sunday.

On Tuesday, Israeli troops seized control of the Palestinian side of the Rafah crossing between Gaza and Egypt after launching an incursion into the eastern sector of the city.

The United Nations and Israel's staunchest ally the United States both condemned the closure of the two crossings which are a lifeline for civilians facing looming famine.