Two South Korean hospitals are conducting experimental treatment on patients with Middle East respiratory syndrome, injecting them with blood plasma from recovering patients, the Health Ministry said on Tuesday as four new cases were reported.

The procedure has been used on two consenting MERS patients in addition to regular care, the ministry's head of public health policy, Kwon Jun-wook, said at a media briefing.

"There is insufficient clinical basis about the result of plasma treatment among experts in the country," Kwon said, but added: "The ministry has deep confidence in the medical staff on the direction of the treatment."