The Hague (AFP) - A 91-year-old Dutch man honoured by Israel for shielding a Jew from the Nazis has handed back his medal after six of his relatives were killed in a Gaza air strike.

Henk Zanoli returned his Righteous Among the Nations award to the Israeli ambassador in The Hague this week after an Israeli F-16 destroyed his great niece's Gaza home, killing all inside.

"It is with great sorrow that I am herewith returning the medal I received as an honour and a token of appreciation from the State of Israel for the efforts and risks taken by my mother and her family in saving the life of a Jewish boy during the German occupation," Zanoli said in a letter dated Monday.

According to Zanoli's letter addressed to the Israeli ambassador, the bomb dropped by the Israeli military on July 20 during its massive Gaza offensive, flattened a four-storey building at the Bureij Refugee Camp, killing all inside.

"The great-great grandchildren of my mother have lost their grandmother, three uncles, an aunt and a cousin at the hands of the Israeli military," Zanoli said in the letter, published by liberal Israeli newspaper Haaretz and widely circulated in the Dutch media.

"It is particularly shocking and tragic that today, four generations on, our family is faced with the murder of our kin in Gaza. Murder carried out by the State of Israel," Zanoli said.

The Israeli Embassy in The Hague on Friday confirmed it was "familiar with the issue," but declined to comment or give details.

The nonagenarian was too frail to deliver the letter in person, but instead sent it, with the medal, to the Israeli embassy in The Hague -- the same place he received the accolade three years ago.

"For me to hold on to the honour granted to me by the State of Israel under these circumstances, would be an insult... to those in my family, four generations on, who lost no less than six of their relatives in Gaza," Zanoli said.

Zanoli's family were outspoken opponents of the invading Nazis and his father was murdered in Mauthausen concentration camp. Zanoli's own brother-in-law was executed in the dunes outside The Hague for being in the Dutch Resistance.

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The Righteous Among the Nations is an honour accorded by Israel to non-Jews who risked their lives to protect and save Jews during the Holocaust.

Almost 2,000 Palestinians, most of them civilians, have been killed in Israel's withering offensive on the isolated Gaza Strip, aimed at ending militant rocket fire.

"The actions of your state in Gaza these days have already resulted in serious accusations of war crimes and crimes against humanity," wrote Zanoli.

"As a retired lawyer, it would be no surprise to me that these accusations could lead to possible convictions if true and unpoliticized justice is able to have its course.

"What happened to our kin in Gaza will no doubt be brought to the table at such a time as well."