Two men who allegedly caused a fatal car accident in Hokkaido last year that killed four of a five-member family and seriously injured one, denied charges of dangerous driving as their trial opened Monday.

Prosecutors said construction worker Ryuji Tanikoshi, 28, and Ryuichi Komi, 27, unemployed were racing when Tanikoshi, who was driving under the influence of alcohol, hit the family's minivehicle. One of the victims died after being thrown out of the car and then dragged by Komi's vehicle for more than 1 km.

The focus of the trial is on whether the Sapporo District Court will acknowledge the rare charge of conspiring in dangerous driving resulting in death and injuries.

At Monday's session, the two defendants said they did not conspire and also denied the prosecutors' claim that they intentionally ignored a red light.

Tanikoshi's lawyer said he missed the red light because he was searching for his sunglasses, despite the accident occurring at night on June 6, 2015.

According to his lawyer, Komi fled the crash scene due to panic, as he knew he had been driving under the influence of alcohol. The lawyer added that Komi did not notice he was driving with a victim trapped underneath his vehicle.

Koichi Nagaoke, 44, his wife, Fumie, 44, their eldest daughter, Megumi, 17, and son, Shota, 16, who was dragged by Komi for about 1.5 km, were all killed in the accident.

The youngest daughter, Hikari, 13, was seriously injured.

In their opening statement, prosecutors said that Tanikoshi and Komi often raced and caused the accident by ignoring a red light at an intersection in the city of Sunagawa.

Tanikoshi was driving at around 170 kph and Komi at 130 kph, the prosecutors said.