A Palestinian woman who was seriously wounded in a West Bank arson attack that saw her 18-month-old son Ali burned to death died on Sunday, more than a month after the incident that also killed her husband.

Reham Dawabsheh's condition took a turn for the worse on Saturday after nearly five weeks on life support at the intensive care unit of Sheba Medical Center, Tel Hashomer. She suffered third-degree burns on 90 percent of her body during the firebomb attack in the West Bank village of Duma in July.

Dawabsheh, whose 27th birthday was on Sunday, was a teacher at the Duma elementary school. The funeral will be held at her village on Monday afternoon after an autopsy is performed on the body at the An-Najah University Hospital in Nablus.

"The death of Reham Dawabsheh is heartbreaking," MK Aida Touma-Suliman (Joint List) said on Monday morning. "[Our] thoughts go out to little Ahmed, the sole survivor of a family that was burned in flames of hatred and evil," she said.

Touma-Suliman blamed Israeli policy for the deaths and said that "the murderers are still on the loose and terror and hate crimes against Palestinians continue to happen."

Her husband, Sa'ad, died a week after the attack from the burns he sustained in the incident. Their four-year-old son Ahmed, the sole survivor of the family, suffered second-degree burns on more than 60 percent of his body. He is hospitalized at Tel Hashomer.

UN envoy to the Middle East Nickolay Mladenov expressed concern on Monday over what he described as Israel's "lack of progress" in apprehending suspects in the attack. In a statement, he called "for justice."

The arson attack, that has been attributed to Israeli extremists and was labeled Jewish terror by top Israeli officials, fueled unrest in Israel and the Palestinian territories and prompted the government to crackdown on far-right extremists.