At least 31 people were injured in a traffic accident involving many vehicles in a Turkish motorway tunnel.

According to the authorities, the condition of two injured people was initially critical.

17 people had to be hospitalized, Turkish Health Minister Fahrettin Koca said on Twitter on Saturday.

The mountain tunnel in the northwestern province of Bolu lies on one of the country's busiest routes, the Anadolu Highway O-4, which connects Turkey's largest metropolis, Istanbul, with the capital, Ankara.

As the state broadcaster TRT reported, a total of 18 vehicles were involved in the accident, including buses, trucks and cars.

The tunnel has been blocked.

According to TRT, the cause of the accident was initially unclear.

The driver of a van lost control of the car and other vehicles drove up, Bolu district governor Ahmet Ümit told the broadcaster.

After recent heavy snowfall, the authorities in the north of the country called on drivers to be particularly careful and stay away from the roads as much as possible.