A bus swerved off a major road and crashed in Croatia early on Sunday, killing 10 people and injuring at least 45 others, some of them seriously, officials said.

The crash happened near the town of Slavonski Brod on the highway between the capital, Zagreb, and the Serbian border at around 6am local time.

Photos from the scene showed the bus on its side in the grass near the edge of the road.

Firefighters and rescuers could be seen around the vehicle, while traffic on the highway was halted.

Police said the bus had Kosovo licence plates and was on a regular route from Germany to the Kosovan capital, Pristina, which is located south of Serbia.

The cause of the crash was not immediately known.

Officials said the bus was carrying 67 passengers, including children, and two drivers.

Local police chief Franjo Galic described the crash as “one of the worst accidents I have ever seen”.

The 45 casualties were taken to hospital in Slavonski Brod. Hospital chief Josip Samardzic said eight people were seriously hurt.

Health Minister Vili Baros later said 15 of the passengers were minors and that one girl had been seriously injured.

Croatian Prime Minister Andrej Plenkovic expressed “sadness and grief” and extended his condolences to the relatives of those who died in the crash and the people of Kosovo.

“We hope the injured will recover,” he tweeted.

Kosovo sent its interior minster to Croatia, as top officials offered condolences to the families of the victims and expressed hope for the swift recovery of the injured.

President Vjosa Osmani, who is in Tokyo for the Olympic Games, spoke of her sorrow in a message on Facebook.

“With our heart and in spirit, we are close to the families who lost their loved ones in this tragedy,” she said. “It is an indescribable pain and a great loss.”

The highway where the crash happened is a key traffic artery through Croatia which is busy over the summer because of tourism and foreign workers travelling home from Western Europe.