Russian investigators Sunday interrogated the hospitalised driver of a truck that ploughed into a packed passenger bus outside Moscow killing 18 people and injuring dozens more.

Officials said the injuries were particularly severe as the truck was carrying gravel which poured onto the passengers in the bus and then covered the roadside.

The accident Saturday afternoon was one of the deadliest road tragedies in Moscow, whose traffic-clogged roads have become ever more dangerous in recent years.

According to preliminary information, the truck hit the bus after it turned onto a main road, smashing the bus into two with the force of the crash.

The driver -- an Armenian citizen who had been repeatedly warned this year for traffic violations -- survived the crash is in "satisfactory" condition in hospital, which "allows the investigation to work with him," the head of the Moscow health department Georgy Golukhov told the Interfax news agency.

More than 60 people were injured in the accident with 32 remaining in hospital overnight for treatment, the health ministry said. A dozen victims were said to be in a serious condition.