Human rights groups launched a court fight Tuesday challenging the U.K. government’s decision to supply parts for F-35 fighter jets, saying they are being used by Israel in Gaza in violation of international law.

The legal challenge in the High Court alleges that the government is breaking domestic and international law and is complicit in atrocities against Palestinians by allowing essential components for the warplanes to be supplied to Israel.

“There’s such clear evidence of the use of weapons parts from the U.K. being used in war crimes, including in genocide,” Sacha Deshmukh, chief executive of Amnesty International UK, said at a rally outside the Royal Courts of Justice in London. “Until this case reaches its judgment, right now as we speak, there are significant human rights violations being delivered by British-made weapons and bombs.”

The government said in September that it was suspending about 30 of 350 existing export licenses for equipment deemed to be for use in the conflict in Gaza because of a “clear risk” that the items could be used to “commit or facilitate a serious violation of international humanitarian law.” Equipment included parts for helicopters and drones.

But an exemption was made for some licenses related to components of F-35 fighter jets, which have been linked to Israel’s bombardment campaign in the Gaza Strip.

Rights groups argue that the United Kingdom shouldn’t continue to export parts through what they call a “deliberate loophole” given the government’s own assessment of Israel’s compliance with international humanitarian law.

Palestinian human rights organization Al-Haq and the U.K.-based Global Legal Action Network, which brought the legal challenge, say the components are indirectly supplied to Israel through the global spare parts supply chain.

U.K. officials have argued that stopping the export of F-35 fighter jet components would endanger international peace and security.

Compared to major arms suppliers such as the U.S. and Germany, British firms sell a relatively small amount of weapons and components to Israel.

The Campaign Against Arms Trade nonprofit group estimates that the U.K. supplies about 15% of the components in the F-35 stealth combat aircraft, including its laser targeting system.

“British-made F-35s are dropping multi-ton bombs on the people of Gaza, which the U.N. secretary-general has described as a ‘killing field,’” said Charlotte Andrews-Briscoe, a lawyer for the Global Legal Action Network.

“The U.K. government has expressly departed from its own domestic law in order to keep arming Israel. This decision is of continuing and catastrophic effect,” she added.

The hearing is expected to last four days and a decision is expected at a later date.

(AP)