Saudi Arabia and Qatar have not reported any coronavirus cases, but the other four Gulf Arab states have.
The virus has infected about 80,000 people worldwide and killed more than 2,800, the majority in China where the outbreak began late last year.
The number of new infections inside China was overtaken by new cases elsewhere for the first time on Wednesday, with Italy and Iran emerging as epicentres of the flu-like illness.
Kuwait and Bahrain recorded more cases on Thursday, all in people who had visited Iran, bringing their totals to 43 and 33, respectively. Oman has diagnosed four cases and the United Arab Emirates, a main air transit hub, has reported 13.
Pilgrimage is big business for Saudi Arabia, which hosts the two holiest sites of Islam in Mecca and Medina, and is the backbone of a plan to expand tourism under Crown Prince Mohammed bin Salman's ambitious economic reform agenda.
Some 2 million pilgrims are expected in late July for the week-long haj, the world's largest annual gathering of Muslims.
"It all depends on the duration of the ban. If it's a long one, it can have more of an impact as Ramadan is two months away," said John Sfakianakis, chief economist at Gulf Research Center.
The Saudi Foreign Ministry said the suspensions were temporary but provided no timeframe. Entry is also suspended for visits to the Prophet's Mosque in Medina.
"Protecting the pilgrims ... and the sacred sites from the arrival of this disease is very important," Health Ministry spokesman Mohammed Abdelali said after government officials met to discuss preventative measures.
"Saudi Arabia feels a sense of responsibility, therefore we took these temporary decisions which will constantly be reviewed."
AIRPORT CONFUSION
In Indonesia, Joko Asmoro of the Association of Muslim Haj and Umrah Organizers told Reuters 150,000 to 200,000 Indonesian pilgrims could be affected by the suspension over the next month. Malaysia, with 23 recorded cases of coronavirus, advised its citizens to postpone visiting the kingdom for now.
Saudi Arabia's benchmark index fell 1.1% on Thursday, weighed down by tourism-related firms Jabal Omar Development, Seera Group, and Al Hokair Group.
The country's top tourism official said this week 400,000 tourist visas had been issued since they were introduced last year for 49 countries as part of efforts to boost non-oil revenue.
The Foreign Ministry did not specify which states would be impacted by the tourism restrictions, but said health authorities would determine where the outbreak constituted a danger.
In the hours after the announcement, there was confusion at airports abroad with flights to Saudi Arabia about who was eligible to travel. In Beirut, passengers without Saudi residency were barred from boarding.
UAE-based Emirates and flydubai, citing Saudi directives, said they would no longer carry passengers with tourist visas from China, Japan, Italy, Iran, India, Pakistan and a number of other countries.
It was unclear on what basis those states were identified and whether they referred to travellers' nationality or their departure location. Saudi government spokesmen did not respond to requests for comment.
Iran has the highest number of deaths from the virus outside China, reporting 26 deaths and 245 infections.
Several of Iran's neighbours have closed their borders and banned flights over the outbreak. Bahrain said it had halted flights to Iraq and Lebanon. The UAE said parents must declare if children or close relatives have travelled in the past four weeks to several Asian countries, Italy or Iran.
Qatar postponed the Doha Interfaith Dialogue Conference due on March 3-4, without giving a reason. Two sources said it was over coronavirus fears. Qatar's government did not respond to a request for comment.