Human rights advocates have reacted with outrage after some restaurants in Saudi Arabia put up signs forbidding women not accompanied by a male guardian from entering the premises.

Members of the National for Human Rights (NSHR) asked the restaurants to take down the signs, which read "single women are not allowed", claiming that they are "illegal".

NSHR spokesman Khalid Al-Fakhri explained that the signs were put up at the owners' requests and not the authorities and women are not required to be accompanied by a male guardian when they go to restaurants.

"These signs are against the law and reflect the personal opinions of the restaurant owners," he said. "Restaurants should come up with alternative solutions if its customers are behaving inappropriately."

However, a manager of one of the restaurants that have banned unaccompanied women, defended the decision in an interview with the daily Al-Hayat.

"We put up these signs because we have seen numerous incidents of flirting taking place inside the restaurant," he said.

"We'll only remove these signs when we make sure such incidents never happen again on our premises because such type of behaviour negatively impacts our business."

According to the Gulf News, a local blogger justified the ban by saying that women behaved in "a shocking way".

Describing the behaviour of one unaccompanied woman in a restaurant, the blogger wrote:

"She would come in alone and focuses on her mobile from which emanates loud music.

"She then takes out a cigarette and upsets other guests who may call in the Commission for the Promotion of Virtue and Prevention of Vice. This could cause problem for the restaurant.

"So the best thing is to keep women away from restaurants unless they have a male custodian. That way the restaurant is not shut down because of the misbehaviour of an adolescent or mentally unstable woman."

However, several Saudis condemned the decision which is seen as "discriminatory" against women.

A female citizen told Al-Hayat that restaurants and cafes are the two main recreational places for women in the country.

"If they're going to ban us from entering restaurants, where are we supposed to go?" she said and added that customers should boycott any restaurant that display such signs.

According to the Kingdom's laws, women cannot go out alone as they have to be accompanied by a male guardian, usually a relative.

Among other things, Saudi women are also barred from driving cars, taking part in sport activities and working in jewellery shops.