A fleet of ambulances was called to the scene of one of Bulgaria's worst accidents.

An out of control bus ploughed into a group of people walking up a hill.

[Unidentified Witness]:
"The bus turned left and scattered the people like balls, I can't imagine what went wrong, it killed several people there, in the forest!"

The Interior Ministry claim a technical fault caused the bus to crash as it headed down hill.

There were no passengers on board and the driver was slightly hurt.

Most of the victims were climbing towards the Bakadzhik peak to celebrate Orthodox Ascension Day.

16 died and around 20 others were injured.

[Nikol Kovacheva, Head of Emergency Services Yambol]:
"I have 30 years service, and I never saw such a tragedy."

Bulgaria's Prime Minister interrupted his election campaign to visit the scene of the crash and the President went to visit survivors in hospital.

Friday has been declared a national day of mourning for the victims.