South Korea on Wednesday said it would waive visa fees for visitors from China and Southeast Asia as it struggles to recover from the MERS outbreak which has seen tourist numbers plummet.

The announcement came as the country reported no new cases for a fourth consecutive day in the outbreak of Middle East Respiratory Syndrome which has infected 182 people, killing 33.

The justice ministry said visas which had been already issued would be extended for another three months as South Korea enters its peak tourist season of July and August.

"These measures are aimed to help boost the tourism industry, which has been affected by the MERS outbreak", it said in a statement.

The outbreak has dealt a serious blow to the tourist industry, with the southern resort island of Jeju suffering a 46 percent fall in Chinese visitors in June compared with last year.

Vice tourism minister Kim Chong has warned the country's earnings could be slashed by up to $2.3 billion if the number of foreign travellers drops by 50 percent.

South Korea will waive tourist visa fees, worth $15, from July 6 through to September 30 for those travelling in groups.

They include tourists from China, Cambodia, Indonesia, the Philippines and Vietnam, the ministry said.

The validity of one-off visas issued between March 1 and June 30 would be automatically extended from three months to six months.

More than a million tourists have been issued these visas.

Chinese tourists travelling in groups with Japanese visas will also be allowed to enter South Korea visa-free for stays of up to 15 days, it said.