At least 20 people have been killed and others injured after a Bolivian air force cargo plane crashed in the western city of El Alto, the country's authorities say.

The incident happened at 18:15 local time (22:15 GMT) on Friday as the plane was arriving at El Alto's airport from the city of Santa Cruz, aviation officials said. It reportedly skidded off the runway and hit nearby vehicles.

The defence ministry later confirmed its C-130 Hercules was involved and that it had been transporting banknotes to the Central Bank of Bolivia. There were eight people aboard the plane, the air force commander said.

Police fired tear gas to disperse crowds allegedly trying to take the scattered banknotes.

Firefighters had given an earlier death toll of at least 15.

Video footage showed the plane on the ground and badly damaged vehicles. In other videos, people could be seen running away from the tear gas and police officers, some holding shields, forming a line. Some in the crowds are seen throwing rocks.

"While news crews were covering the accident, individuals attempting to steal the transported money attacked the press with unusual violence," the National Association of Journalists of Bolivia said in a statement.

It said a mobile TV unit was "directly targeted", while other journalists "were attacked with stones, suffering serious injuries while carrying out their work".

The government-run Bolivian News Agency reported that at least a dozen people were arrested for stealing banknotes.

"I want to make it clear to those who are trying to take money from the plane involved in this tragedy that this money has no legal value since it has not been issued by the Central Bank and does not have a serial number, and that attempting to use this money is a crime," the Minister of Defence, Marcelo Salinas, said.

"We also ask all those who are engaging in acts of vandalism in this area to refrain from doing so and to respect the mourning and grief we are experiencing at this difficult time."

Bolivia's Air Force commander Sergio Lora confirmed there were eight crew members on board the plane "including cargo personnel and flight crew".

Bolivia's health ministry said 31 people were injured in the incident. It also issued an urgent appeal for blood donations.

El Alto International Airport was temporarily closed following the crash.

"My sister told me that she was in the car when the plane crashed. The plane's tire fell on the car, and my sister was injured because the impact of the tire hit her on the head, so we rushed her to the hospital," a man told the Reuters news agency.

It was not immediately clear what caused the crash, but some witnesses said the weather at the time was treacherous.

"A heavy hailstorm" was falling and "there was lightning" when the plane went down," a woman whose car was struck by the aircraft wreckage told the AFP news agency.

An investigation into the incident is under way.