A Dutch-Palestinian seeking justice for his relatives killed in the air strike urged the court to go ahead with a trial for war crimes.

This preliminary hearing, to determine whether or not it should try the case, started as Israelis go to the polls to elect a new government -- with Gantz a leading candidate for the prime minister's post.

Gantz, 60 was the chief of general staff of the Israeli defence force at the time of the Gaza bombing as part of Operation Protective Edge, in which Ismail Ziada said six of his relatives were killed.

The second defendant is former Israeli air force chief Amir Eshel, 60.

"I am seeking justice," Ziada told judges at The Hague's District Court. He would not get a fair hearing before an Israeli court, he argued, because it "discriminated against Palestinians seeking accountability for war crimes".

Ziada's mother, three brothers, a sister-in-law, a young nephew and a friend were killed in the strike on Bureij refugee camp in Gaza on July 20, 2014.

Israel said it launched Protective Edge at the time to stop rocket fire against its citizens and destroy tunnels used for smuggling weapons and militants.

"As a Palestinian, my client has no access to a partial and independent judge" before an Israeli court, Ziada's lawyer Liesbeth Zegveld told the judges.

"In other words, it's impossible for him to take his claim anywhere else," she said.

During an emotional statement, Ziada showed pictures of his dead relatives, telling the judges "much depends on the outcome of this judicial process", which he called a "David versus Goliath" legal battle.

Zegveld argued that the case could be heard under Dutch law, which says that it has universal jurisdiction in civil cases for citizens who are unable to get justice for war crimes elsewhere.

Ziada's arguments, however, were dismissed by lawyers representing Gantz and Eshel -- who did not themselves attend the hearing.

"It is not up to the Dutch court to judge military actions of Israel, just as it is not up to an Israeli court to judge Dutch military actions in Afghanistan, Iraq and the former Yugoslavia," Thom Dieben told the judges.

"There is no good reason why the plaintiff cannot and have not filed his claim before the Israeli courts," another lawyer, Cathalijne van der Plas, added.

"It is a case that has no connection with the Netherlands and derives from a situation... thousands of kilometres away, and relates to sovereign military intervention by the state of Israel in the context of an authorised military operation.

"The only possible conclusion here is that your court does not have jurisdiction to hear the case," she said.

Judges are expected to hand down a ruling within the next two months.

In total, Operation Protective Edge left 2,251 dead on the Palestinian side, most of them civilians, and 74 on the Israeli side, most of them soldiers.