Israeli Prime Minister Benjamin Netanyahu called Wednesday for the International Committee of the Red Cross to help return civilians and the bodies of soldiers held in Gaza as he met the organisation's head.

"We are concerned about this unbelievable cruelty," Netanyahu said after talks with ICRC president Peter Maurer, who is on a three-day visit to Israel and the Palestinian territories.

Two Israeli soldiers, Oron Shaul and Hadar Goldin, are believed to have been killed in the 2014 war in the Gaza Strip and their remains held by the Islamic movement Hamas which runs the Palestinian territory.

Three Israeli civilians, all said to be mentally unstable, are also believed to have entered Gaza and to be held by Hamas.

The ICRC can help in "retrieving the bodies of our fallen soldiers but also in bringing back to Israel these defenceless, helpless civilians who are held by Hamas against the contravention of all international norms", said Netanyahu.

Maurer, who met with Hamas's hardline Gaza chief Yahya Sinwar on Tuesday, said: "We have a mandate on international law but also on helping people and finding practical ways."

Hamas has fought three wars against Israel since 2008, with the latest in 2014 leaving more than 2,200 Palestinians dead and 73 killed on the Israeli side.