Palestinians mourn the death of their relatives
Palestinians mourn the death of their relatives in RafahReuters

Israeli forces have killed at least 10 Palestinians from two militant groups who had infiltrated southern Israel through a tunnel from Gaza as the death toll since the start of Operation Protective Edge topped 500.

Residents of Kibbutz Nir Am and Kibbutz Erez were told to remain indoors as the Israeli air forces opened fire on the two cells when they were identified in the area. The operation took place as the Israeli Defence Forces (IDF) advanced into the Gaza Strip overnight, despite calls from the UN Security Council for an immediate ceasefire.

Israeli jets and tanks continued to pound the Gaza Strip and killed 25 people from one family in Rafah, near Gaza's southern border with Egypt. Ten Palestinians from another family died in nearby Khan Younis after shells hit their home, according to hospital officials.

Following the overnight raid, the Palestinian death toll reached 484, mostly civilians, while Israel says 18 of its soldiers have died along with two civilians.

Diplomatic efforts are being stepped by the international community to bring an end to the ongoing Israel-Gaza conflict.

The 15-member UN Security Council expressed "serious concern about the growing number of casualties...[and] called for an immediate cessation of hostilities," Rwanda's UN Ambassador Eugene Gasana told reporters.

The diplomatic push comes alongside US Secretary of State John Kerry's expected arrival in Cairo to coordinate the ceasefire negotiations.

Along with Egyptian authorities, Kerry is poised to broker discussions in a bid to stop the fighting between Israel and Hamas.

The White House said Kerry will seek "an immediate cessation of hostilities based on a return to the November 2012 ceasefire agreement," adding that civilians must be protected in both Israel and Gaza.