A lawyer for the captain said he is in an unstable condition after the accident and would like to convey his deep sympathy to the victims' families.

The decades-old Hableany carrying 33 South Koreans and two Hungarian crew members capsized and sank soon after being hit from behind by the Swiss-registered Viking Sigyn.

The collision left seven Koreans dead and 21 people missing, 19 of them also Korean. Seven Koreans were rescued.

Footage from a security camera released by a cruise alliance made up of local tourist boat operators showed that the Viking Sigyn hit the Hableany and disappeared from view before moving back to the accident site. It then resumed its previous course.

South Korean and Hungarian workers carried out joint operations on Saturday to search for the 21 missing people, officials said, but the operations were hampered by high waters and strong currents.

They conducted surface-level searches up to 50 kilometers down the Danube River from the site of Wednesday's disaster.

In response to requests by South Korea and Hungary, Croatia, Serbia, Romania and Bulgaria have also been conducting search operations in parts of the Danube River.

During Saturday's search, the Korean and Hungarian authorities tried to send underwater drones to where the sunken ship lies but failed to do so due to strong currents.

"We brought sonar systems and underwater drones from Austria, the Czech Republic and Norway, but could not use the drones due to excessively strong currents," a South Korean official told reporters.

The search workers also found that the ill-fated ship lies 8.1 to 9.3 meters underwater, deeper than the 6 meters that was initially estimated.

On Saturday, South Korean Foreign Minister Kang Kyung-wha met a 66-year-old South Korean survivor, identified only by the surname Lee, at a hospital in Budapest and later told reporters that it's difficult to say when the victim could be discharged.

Kang said Lee could barely speak due to physical exhaustion following a long trip and the accident.

The hospital officials said Lee is in a stable situation but has not recovered enough to be released and fly back to South Korea.

Alongside the search operations, the Hungarian authorities also plan to resume preparations to salvage the hull of the boat out of the water.

The authorities have been mulling when to begin the salvage operations in earnest, while taking into account the adverse river conditions.

Seoul has formed an emergency response team consisting of 53 people, including staff from the foreign ministry, police, the National Intelligence Service and other agencies, to support search operations and ensure coordination with Hungary.

In Seoul, Vice Foreign Minister Lee Tae-ho presided over a government disaster management session, reiterating the government will put all its effort into searching for the missing.

"We are concentrating all our efforts in all areas, including expanding the scope of search operations and crafting measures to prevent any damage to or loss of bodies during the work to salvage the hull out of the waters and search the vessel," Lee added.

South Korea's presidential office Cheong Wa Dae has operated its crisis management center around the clock to check on progress in the search operations in Budapest.

In a message to South Korean Interior Minister Chin Young, Hungary's Interior Minister Sandor Pinter said that his government will make all-out efforts to search for the missing South Koreans and investigate the cause of the sinking.

In a reply, Chin called for active cooperation in supporting the search operations and handling and transporting the deceased. (Yonhap)