At least 21 people died when a passenger train derailed in eastern Iran on Wednesday, Fars news website reported, while 60 passengers were seriously injured.

The head of the country’s emergency services said 15 injured passengers are in critical condition in hospitals in southern Khorassan province, according to ISNA. Other officials have put the number at around five people.

The train with 430 passengers and crew travelling to the city of Yazd collided at 5:30 am local time with an excavator before going off the rails 50 km (30 miles) from the city of Tabas, where it began its journey, a railway official told state news agency IRNA.

"Ten ambulances are at the accident scene and another 12 are on their way," the crisis management chief of the province of South Khorasan told the agency.

One reporter from Tehran tweeted that Iran has invested very little in maintaining and modernizing its rail system in the past 15 years.