The virus, believed to be transmitted from camels to humans, has infected at least 17 people in Taif since September 5, a ministry statement said.
That is about half of the 38 cases reported in the kingdom since that date.
"MERS-CoV remains a significant health threat in Saudi Arabia," the ministry said.
MERS has hit the kingdom hardest, killing 333 people since June 2012. The virus has also appeared in about 20 other nations.
According to data on the health ministry's website, five of the nine MERS deaths since October 16 were in Taif.
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Health officials are "particularly concerned about breaking the chain of transmission in Taif, where a cluster was identified in September," the ministry said.
Primary cases in Taif involved people who had unprotected contact with camels and then came into contact with others, including healthcare workers, it added.
"The situation in Taif is still under investigation and we expect to see more cases in the coming days and weeks," said Anees Sindi, deputy commander of the health ministry's command and control centre, which coordinates the response to MERS.
The ministry reiterated that proper hand-washing and "coughing etiquette" are essential steps to reduce the infection risk.
"Members of the public are also urged to avoid contact with camels and refrain from consuming raw camel milk or undercooked camel meat," it said.
There have been 780 confirmed cases of MERS in the kingdom since June 2012.