The Islamist Hamas group ruling the Gaza Strip is to begin deducting the previously optional "zakat" or alms from businesses and individuals during Ramadan, it said on Tuesday.

The Zakat Foundation created by Hamas will begin deducting the money during the Muslim holy fasting month that begins on Thursday or Friday "from the taxes on firms," its chief Rami al-Khatib told AFP.

"This will begin as an optional measure before becoming obligatory," he said, adding that the authorities would strive "not to increase the amounts" to be deducted from individuals.

Khatib said the aim was to "collect funds for zakat and distribute it to the poor."