"I request that you urgently take exhaustive measures to investigate the circumstances of this tragic incident and to hold those responsible liable," its says in a letter addressed to Prosecutor-General Oleksandr Medvedko, the president's press service reported on Sunday.
Yushchenko instructed the head of Rivne regional state administration, Viktor Matchuk, "to take urgent organizational measures for providing all-round aid to the families of the victims".
As reported, six people were fatally injured on Saturday night by the passing Kiev-Ivano-Frankivsk passenger train No 43. The young people aged 17-20 were returning home to the village of Zdovbytsa along the railway line from a club in the neighbouring village.
At 10:23 GMT on 27 January, Interfax-Ukraine quoted the state railway administration Ukrzaliznytsya as saying the railway was not responsible for the incident.
"When he noticed people on the tracks, the driver of train No 43 sounded a warning signal and applied the brakes. But in line with the timetable, the train was travelling at 90 kilometres (56 miles) an hour and the braking distance was about 900 metres (2,950 feet), so it was not possible to avoid hitting the people," it said in a statement.
Source: BBC Monitoring