PANAMA CITY: Panama's president declared a day of mourning Friday after at least 24 people were killed when a bus collided head-on with a large dump truck in the country's capital.

An all-terrain vehicle was also involved in the accident, which occurred at 10:45 pm Thursday (0345 GMT Friday), officials here said. At least 30 people were injured.

"I've never seen a spectacular accident like this," President Ricardo Martinelli said after visiting the crash site.

"The saddest thing was to hear mobile phones ringing inside the bus -- desperate relatives trying to call their loved ones to find out why they had not arrived at home," a visibly shaken Martinelli said.

Witnesses said that the crash was so loud it was heard several kilometers (miles) away.

Police gave an initial death toll of 22, with 10 injured.

The accident could have resulted from high speed under poorly lit conditions, officials said.

Martinelli said that most of the victims were construction workers or worked at a local supermarket.

People living close to the crash site recently protested the lack of road safety in the area after a woman was killed when the taxi she was traveling in slammed into an ambulance.