RIYADH, May 12 -- Saudi Arabia's registered number of Middle East Respiratory Syndrome (MERS) coronavirus cases increased to 491 on Monday, including 147 deaths, after adding six new cases and five more deaths, the Health Ministry said.

Two of the new cases are in stable condition, while the other four are in critical condition and receiving treatment in ICU, the ministry said, adding that three of the new cases are from Riyadh, two from Jeddah and the rest one from Medina.

Meanwhile, the ministry said six cases have fully recovered by Monday.

The coronavirus was first discovered in mid-2012 in an old man with acute pneumonia and renal failure. It has spread from Gulf countries to North Africa, Southeast Asia and Europe, killing more than a hundred people and infecting hundreds of others.

Saudi Arabia has retained the highest number of MERS cases in the world, registering new cases and deaths almost on a daily basis.

Earlier in the day, the Health Ministry announced an early preparation to assure the availability of medics, medical equipment and medicines during this year's Hajj season.

The ministry has earlier recommended the Hajj Ministry not to allow elderly and pregnant women to perform hajj this year.