JERUSALEM - An Israeli court on Tuesday sentenced a Palestinian aid worker convicted of funnelling funds to Gaza militant group Hamas to six more years in jail on top of the six years he has already spent in detention.

Mohammad El Halabi, head of Gaza operations for aid group World Vision, was convicted in June of being a member of a terrorist organisation. Throughout his incarceration and trial, El Halabi has denied all the allegations.

World Vision and rights groups have denounced his conviction and trial, which they said was not fair and transparent.

In a detailed ruling published on Tuesday, the Beersheba District Court sentenced El Halabi to 12 years in jail, subtracting his six years of detention so far. Halabi's lawyer said he would appeal.

"I feel disappointed at the world, which failed to free an innocent man," said El Halabi's father, Khalil.

The court said Halabi, 44, was a member of Hamas, which Israel and the West designate as a terrorist organisation, and had abused his World Vision job by using its money to fund Hamas weapon deals and secure equipment for militants.

"It can be said with certainty that the possible damage of the defendant's actions was significant with the potential to cause devastating and even fatal damage to the security of the State of Israel and its residents," the court said.

World Vision has said an independent audit found no evidence of wrongdoing or of funds missing. The court mentioned sums of up to $30,000 for numerous deals, totalling "millions".

"The arrest, six-year trial, unjust verdict and this sentence are emblematic of actions that hinder humanitarian work in Gaza and the West Bank. It adds to the chilling impact on World Vision and other aid or development groups working to assist Palestinians," spokeswoman Sharon Marshall said.

Drawing condemnation from the United Nations and some European states, Israel has cracked down on humanitarian groups it says channel funds to Palestinian militants.