BUDAPEST: Hopes for survivors were fading on Thursday after one of the country`s worst boat disasters that left seven South Korean tourists dead and 21 others missing.

The Mermaid sightseeing boat capsized and sank in just seconds after colliding with a huge passenger river cruise ship on the Danube in the heart of Budapestin driving rain on Wednesday evening.

Army boats were scouring the murky waters of the Danube as dozens of people looked on, more than 20 hours after the accident in the chilly and fast-moving river.

At the time of the collision, most passengers were sheltering from heavy rain in the boat`s interior, Mihaly Toth, a spokesman for Mermaid owner Panorama Deck told weekly magazine HVG. `It was not an easy place for so many people to escape f rom in a short space of time,` Toth said.

Seven passengers survived but the chances of any of the other tourists or crew being found were now `very slim`, Toth said.

Thirty-five people were on board the Mermaid, most of them South Korean tourists including a six-year-old girl who was travelling withher mother and grandparents and remains missing.

`The current was so fast and people were floating away but the rescue team did not come,` a rescued 31-year-old woman identified only by her surname Jung told South Korea`s Yonhap news agency.

The 26-metre Mermaid, which sank near Hungary`s parliament building, was dwarfed by the vessel it collided with the 135-metre four-storey Viking Sigyn `longship` which had about 180passengerson board.

Police said they have launched a probe into `criminal negligence` and were questioning the Sigyn`s Ukrainian captain.The tragedy comes five years after the Sewol disaster in South Korea in which more than 300 people, mostly children, perished when a ferry capsized in April 2014.

In Budapest, army divers joined police in the search operation, but it has been complicated by high river levels and a strong current after weeks of heavy rainf all.

Three bodies have been found several kilometres south of the disaster site, police said.

The Mermaid was regularly serviced and had no apparent technical faults, Toth, the spokesman for its owner Panorama Deck toldHungarian news agency MTI, adding that it was on `a routine sightseeing trip`.

Lee Sang-moo, chief operating officer of Very Good Tour which organised the trip for the South Koreans, said most of the passengers were in their 50s and 60s, with the oldest a man in his early 70s.

`Most dif ficult moments` Orban sent a condolence letter to Prime Minister Lee Nak-yeon, and sought to ensure his counterpart that Hungary was making every possible effort to find survivors, Hungarian government spokesman Zoltan Kovacs said.

`We stand together with the people of South Korea in these most difficult moments.

The accident happened on a popular part of the River Danube for pleasure trips, from where passengers can view the city and parliament building illuminated at night.

Dozens of small sightseeing boats ply the river through Budapest every day. Larger river cruise boats travelhng on the Danube between Germany and the Black Sea typically spend several days moored in the capital.-AFP