Sheikh Abdullah al-Mutlaq, a member of the Council of Senior Scholars, said women should dress modestly, but this did not have to mean wearing the abaya.

Saudi women are currently required to wear the garment by law.

The cleric's intervention comes amid moves to modernise Saudi society and relax restriction on women.

"More than 90% of pious Muslim women in the Muslim world do not wear abayas. So we should not force people to wear abayas," Sheikh Mutlaq said on Friday.

It is the first time a senior cleric has made such a statement, which may form the basis of Saudi law in the future.

What has the reaction been?

Sheikh Mutlaq's intervention has generated intense reaction online, with people expressing both support and opposition.

"The abaya is a matter of tradition in one of our regions and has become applicable to all. It is not an issue of religion," wrote Twitter user Mashari Ghamdi.

"Even if one hundred fatwas have been issued, I swear to God I will never leave my abaya. Over my dead body. Girls, do not listen to the fatwas…" wrote twitter user @Kooshe90.

Women who do not wear the abaya in places where they may be seen by men who are not related to them face being chastised by the religious police.

In 2016, a Saudi woman was detained for removing her abaya on a main street in the capital of Riyadh, Reuters news agency reported.

However in recent years Saudi women have begun wearing more colourful abayas that contrast with the traditional black, and open abayas worn over long skirts or jeans are also becoming more common in some parts of the country, Reuters says.

What is the background?

Sheikh Mutlaq's intervention follows earlier moves to modernise Saudi society, part of a social reform plan spearheaded by Saudi Arabia's Crown Prince Mohammed bin Salman, who has pledged to transform the country with the government's Vision 2030 programme.

It is aimed at giving more freedom to Saudi women, who face strict gender segregation rules, and follows the historic lifting of a driving ban in September 2017.

In the same month, women were allowed to participate in Saudi Arabia's National Day celebrations for the first time.

Last month women were permitted to watch football live in stadiums in some cities.

Last year, Saudi Arabia also announced that it was lifting a ban on commercial cinemas that has lasted more than three decades. The first cinemas are expected to open in March this year.

In December, thousands of women cheered and rose in a standing ovation at the first public concert performed by a female singer in the country.

Up until now, such sports and entertainment venues have been men-only areas.

What can Saudi women still not do?
There are many things that Saudi women are unable to do without permission from the men in their lives.

These things include, but are not limited to:

Applying for passports
Travelling abroad
Getting married
Opening a bank account
Starting certain businesses
Getting elective surgery
Leaving prison

These restrictions are down to Saudi Arabia's guardianship system, which has aligned the country with a strict form of Sunni Islam known as Wahhabism.

Under the system, every woman must have a male companion with her in public, usually a close family member, who has authority to act on her behalf in these circumstances.

This has helped create one of the most gender unequal countries in the Middle East.