A prominent Saudi cleric on Wednesday endorsed Valentine's Day calling it a "positive social event" that was not linked to religion.

The comment from Ahmed Qassim Al Ghamdi, former chief of the religious police in the holy city of Makkah, comes as 32-year-old Crown Prince Mohammed bin Salman pursues a far-reaching liberalisation drive that has upended years of conservative tradition.

"It is a positive social event and congratulating people for it is not against sharia (law)," Ghamdi told Saudi-owned Al Arabiya television.

"It is an act of kindness to share greetings on Western national and social holidays, including Valentine's Day, exchange red roses with others, as long as it is towards peaceful people who do not share animosity or are being at war with Muslims."

In recent years, Saudi Arabia launched a series of reforms. Prince Mohammed, who has vowed to return the country to "moderate Islam", has further cut back the political role of clerics in a historic reordering of the Saudi state.

Florists openly sold red roses and Valentine's Day memorabilia in cities such as Jeddah on Wednesday.