The captain of a vessel that collided with a small tour boat on the Danube in Budapest, resulting in at least seven deaths, has been arrested, police say, BBC reported.

The 64-year-old Ukrainian national was held as a suspect over reckless misconduct in waterborne traffic leading to mass casualties.

The boat carrying South Korean tourists sank seven seconds after the collision during a rainstorm on Wednesday.

Hopes have faded that any of the 21 people missing will be found alive.

A criminal investigation has been launched into the collision, a rare incident on the Danube where navigation is busy but generally safe.

Seven people rescued alive were suffering from hypothermia but stable, an ambulance spokesman said.

South Korea’s foreign minister, Kang Kyung-wha, is due to arrive in Budapest on Friday for a joint press conference with her Hungarian counterpart Péter Szijjártó.