The main gate of the Ritz Karlton hotel in RiyadhFayez Nureldine | AFP | Getty ImagesSaudi Arabia will relax its rules to allow unmarried men and women to share hotel rooms, as the country opens up to international tourism in a bid to diversify its economy.In a Twitter post Sunday, the Saudi Commission for Tourism and National Heritage (SCTNH) said foreign tourists would no longer need to prove they are related to share accommodation while visiting the kingdom. Tourists from overseas will be able to check into hotels by showing their passports, SCTNH added.Saudi nationals will be asked to present a family ID or proof of relationship when men and women check into hotel rooms together. However, all women — including Saudis — will be permitted to stay in hotels alone, provided they show their ID on check-in.The move is drastic for the notoriously conservative Islamic nation, and an abnormality for the wider region.Adultery is a crime in Saudi Arabia that carries severe penalties, with sex outside of marriage punishable by imprisonment, stoning or the death penalty.Even in the United Arab Emirates and Qatar, Saudi Arabia’s more liberal neighbors, adultery is a crime that carries serious penalties including imprisonment and deportation. Unmarried couples are technically banned from sharing hotel rooms in both countries, although the laws are rarely or unevenly enforced, and legislation bans couples who are not married from living together.Allowing women to stay alone in hotel rooms is also a somewhat unprecedented decision from the Saudi government. Women face tough restrictions under Saudi legislation, although they have been granted some rights in recent years, such as the right to drive.Under the kingdom’s guardianship system, women are assigned a male relative whose approval is needed to apply for a passport, get married, or travel abroad.Absher, an app developed by the Saudi government, has digitized the system and asks male users to list any dependent women. The app then allows male guardians to track their dependents and grant or deny them permission to travel.Saudi Arabia’s new tourist visas were rolled out at the end of September as part of the government’s Vision 2030 agenda. The kingdom is aiming to increase the economic contribution of tourism from 3% to 10% of GDP by 2030. Prior to the visa’s release, the country relied on tourism from religious pilgrims.— CNBC’s Natasha Turak contributed to this article.