South Korea's MERS outbreak is growing as the number of stricken individuals placed under quarantine increased to 1,369 on Wednesday, according to World Health Organization.

Five new MERS cases, contracted within hospitals, were confirmed by the Korean Centers for Disease Control and Prevention, shooting the number up to 35 people, USA Today reported.

South Korea's Health Ministry said on Thursday that three people have died of MERS, making it the largest number of cases recorded outside Saudi Arabia since it first emerged in 2012.

South Korean authorities said the number of quarantined people has doubled due to possible exposure, but they refused to identify the hospitals where MERS cases have been verified, The New York Times reported.

All the reported cases of MERS are from medical staff members, patients and visitors of these hospitals.

Reports said that more than 900 schools and kindergartens have been temporarily closed as quarantine is being done.

"Initial reaction for new infectious diseases like MERS is very important, but there were some insufficiency in the initial response, including the judgment on its contagiousness," South Korean President Park Geun-hye said, according to CNN.

The first South Korea MERS case was reported on May 20 about a man who traveled from Saudi Arabia, Qatar, the UAE, and Bahrain returned to South Korea. But WHO noted that the person had not been ill during his travels.

The 40-year-old man developed symptoms on May 20, according to WHO. The patient was then admitted to four hospitals until he was tested positive for MERS on May 31.

Health officials said two South Korean patients died on Monday and three other were in serious condition.

WHO said there are more 1,179 cases of MERS worldwide and almost 442 deaths have been recorded so far.