Saudi Arabia has been criticised by a human rights monitoring group for not exempting Syrian and Yemeni refugees living in the kingdom from taxes it has imposed on expatriates.

Riyadh introduced the taxes on July 1 for dependents of expatriates in the country and they will gradually increase until 2020.

Expatriates have to pay 100 Saudi Riyal ($26) a month for each dependent on top of the existing fees and expenses. Some companies cover those costs.

Euro-Med said in a statement released on Wednesday that the decision not to exempt Syrians and Yemenis from the tax will have a negative impact on their living conditions.

"People displaced by war who have no means of subsistance cannot be equal to others coming to the country for tourism, work or studies and who fall under the expats category," the statement said.

"The Kingdom of Saudi Arabia must take into account the humanitarian and living conditions of the newcomers to the kingdom, Syrians and Yemenis in particular, who entered the kingdom in search of safety for them and their children.

"Their inclusion in such a decision constitutes an important obstacle for them to continue living in the kingdom."

The fees is expected to be paid annually when visa is renewed.

According to the United Nations, more than five million Syrians, including at least 2.4 million children, have fled their country since the civil war started five years ago.

The UN refugee agency (UNHCR) estimates that more than 2.4 million Yemenis have fled their homes to elsewhere in the country, and 120,000 have sought asylum in other countries.