The Gaza Strip's water provider on Wednesday urged the area's 1.5 million residents to boil their drinking water, blaming a shortage of purifying chlorine on Israel's blockade of the strip.

Israel Defense Forces said no Palestinian request for chlorine was made until Wednesday, and it was urgently trying to arrange a new shipment into Gaza.

The Coastal Municipality Water Utility informed residents that sanctions have left Gaza without equipment and supplies needed to maintain the water system and chlorine deliveries stopped on January 21. More than one-third of Gaza's water supply is now untreated, said deputy director Maher Najjar, amid concern over a health disaster due to possible contamination. He appealed to the international community for help.

Most Gaza residents do not have regular water supplies because of a shortage of fuel used to pump water. Many already use filters or buy bottled water because the quality of tap water is generally poor.

Israel imposed sanctions on Gaza after militant group Hamas seized power last June and has tightened its blockade in recent weeks in response to repeated rocket attacks on southern Israel by Gaza militants.

Under the sanctions, Israel, the main gateway for Gaza's imports and exports, has allowed only basic humanitarian goods to enter the territory and has reduced fuel and electricity supplies to the strip.

Najjar said 52 of 140 wells used to supply water to Gaza residents were out of chlorine. "I expect by the week's end all the wells will run dry of chlorine," he said.

Nafiz Alia, the utility's chlorine supplier said 65 tons of chlorine were needed per month and the last shipment into Gaza contained 30 tons forcing him to use reserve stock to make up the rest.

An IDF spokesperson said Israel only received a request from the Palestinians for chlorine on Wednesday. "We are doing our best to allow the chlorine to enter the Gaza Strip as soon as possible," the spokesperson said, adding that it's a shame the Palestinians waited so long to notify Israel.

About 100 wells in Gaza lack diesel fuel to power pumps used during frequent power outages. "When the electricity goes out, the water is knocked out as well," Najjar said.

Most Gaza residents who can afford to do so filter Gaza's salty, brackish tap water before drinking it. However, Najjar said that this does not kill the bacteria.

He said the real danger lay in children drinking untreated water.