Police in Italy have arrested two Pakistani nationals for the alleged murder of four migrant workers found dead in a burnt-out minivan, according to Italian media reports.

The vehicle was found at a petrol station near a village in a vast farming area in the southern Calabria region. 

CCTV images showed two people blocking the van's doors from the outside and throwing liquid inside to start a fire. 

Reports said there had been 14 cases of arson involving cars and minivans carrying Pakistanis in recent months in the area, where there are tensions between migrants over the division of farm work and accommodation.

Firefighters were called to the scene of a burning van at around 13:00 local time (11:00 GMT) on Tuesday.

After extinguishing the flames they made the grisly discovery of four charred bodies inside.

The two suspects were later arrested based on evidence from the CCTV footage, the reports said.

Italian media said a fifth man from Afghanistan had survived the attack. He was quoted as saying that the dead included three Afghans and a Pakistani, all working in agriculture.

The survivor told Italian media that he had escaped the burning car by breaking one of the windows.

He said that a dispute had arisen after the two arrested men had demanded transportation money from those in the car, which they had refused to pay. He also alleged that the workers had not been paid for their work in the region's strawberry fields, although they had been given food and lodging.

The killings have shocked Italy. Calabria's regional president, Roberto Occhiuto, said news of the attack "shakes faith in humanity", adding that it was "inhuman".

The CGIL union meanwhile was quoted by Italy's Ansa news agency as demanding action to "combat the abominations of daily life endured by workers, often migrants, in our countryside".