Graffiti at Duma arson site
Graffiti at Duma arson siteFlash 90

A senior United Nations (UN) official expressed concern Wednesday over Israel's failure to bring to justice those behind an arson attack that killed three members of a Palestinian family, including a baby, AFP reports. 

The mother, father and the 18-month-old son of the Dawabsha family died after their house in the village of Duma in the Palestinian Authority (PA) was firebombed in July - allegedly by Israeli Jewish extremists. 

The attacks led to widespread condemnation globally as well as by Israelis and Palestinians, but as yet no one has been charged for the killings.

Nickolay Mladenov, United Nations special coordinator for the Middle East peace process, said the lack of charges was troubling.

"Four months have passed since the arson attack against the Dawabsha family," he said in a statement. "I am concerned by the slow progress and call on the Israeli authorities to move swiftly in bringing the perpetrators of this terrible crime to justice."

Israeli news media reports in recent days have suggested a breakthrough in a case involving Jewish extremism is imminent, but a gag order has prevented details from being published.

The authorities have suggested that some of the suspects may be currently detained under Israel's administrative detention policy, which enables suspects to be held without trial for six-month renewable periods.

Palestinian Arabs claim the murders as a rationale for the recent wave of terror attacks against Jews and Israelis, which have killed 22 since October 1. 

"Amidst the current escalation of violence, it is essential that all firmly and consistently reject terrorism and act decisively to stop hatred and incitement," Mladenov said.