BUDAPEST, Hungary - A Hungarian court sentenced a Ukrainian ship captain to five-and-a-half years in prison on Tuesday over a collision on the Danube in 2019 that killed 25 South Korean tourists and two crew members.

The disaster, on a busy stretch of the river in the heart of Budapest, was Hungary's worst boating accident in more than half a century.

The Mermaid sightseeing boat carrying 33 South Korean tourists and two Hungarian crew members sank within seconds after colliding with the much larger Viking Sigyn river cruise vessel.

Yuri Chaplinsky -- now 68 and at the helm of the larger Sigyn vessel belonging to the Basel-based Viking Cruises company -- was found guilty of misconduct.

However, Chaplinsky was acquitted of 35 counts of failing to provide help during the May 2019 disaster.

Before the verdict, the captain voiced his "immense regret" for the 2019 disaster.

"I can't rest even for a minute because of the memories of this terrible tragedy. I can't sleep at night because of them," he said in front of a packed courtroom.

"I have at least managed to convince the court... that there was no failure to provide help in 35 counts, which would have been a deliberate act," defence lawyer Gabor Toth said after the verdict was read.

Only seven South Koreans could be rescued, while 25 died, along with two Hungarian crew members, including the Mermaid's captain.

A South Korean woman remains missing almost four-and-a-half years after the tragedy.

According to prosecutors, Chaplinsky did not concentrate on his duties for at least five minutes and was unaware of the dangerous proximity of the much smaller Mermaid, failing to slow down and steer away from it or send radio alarm.

He then allegedly neglected his duty to provide help to those who fell in the water or were trapped on board the sunken boat, prosecutors said.

However, in a written statement read out during the trial, which began in March 2020, Chaplinsky stated that he didn't notice the boat and thought it had hit driftwood, according to Hungarian newspaper Blikk.

When he realised what had happened, he went into shock and let the second officer take command.

The Ukrainian's defence lawyer asked the judge to acquit his client of all charges, arguing that the captain of the Mermaid was the only person responsible for the tragedy.