VATICAN CITY (AFP) - Pope Francis on Saturday voiced condolences for the victims of a ferry disaster in South Korea, where 273 people are missing and 29 have been confirmed dead.

"Please join me in praying for the victims of the ferry disaster in Korea and their families," he said in a tweet published on his Twitter account #pontifex.

Pope Francis is due to make a five-day visit in August to South Korea, which has more than five million Catholics - around 10 per cent of the population.

He will be the first pope to visit Asia since John Paul II. His predecessor Benedict XVI did not travel there during his eight-year pontificate.