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Rome -Twelve foreign agricultural workers were killed Monday when the van transporting them during tomato harvest season smashed into a lorry in southern Italy, the Italian fire service said.

All those who died in the crash, which took place near the city of Foggia in Puglia, were non-EU citizens, the fire service told AFP.

It added that three other people including the lorry driver were injured. The cause of the crash is not yet known.

Every summer thousands of labourers from around Europe and Africa work in the area picking tomatoes.

Italian media has reported that the migrants were being taken back to their makeshift homes after their day's work, when their van slammed head-on into a lorry transporting harvested tomatoes.

It was almost like another crash on Saturday, in which four African farm workers were killed and four others seriously injured, also in a collision with a tomato truck.

Although most of those working in the fields in Italy have regular papers, rarely do they receive the benefits and salaries required by law and live in squalid conditions.

They are often at the mercy of day labourer recruiters sometimes linked to organised crime, who operate as intermediaries to farmers who themselves struggle with large retailers forcing down the price of produce.

For years, unions and associations that help migrant workers have called for a public transport system to be created around Foggia for the peak harvest season.

Dozens of African agricultural workers living in one of the area's shanty towns decided to go on strike on Wednesday following Saturday's accident, the representative of the USB union, Aboubakar Soumahoro ,told AFP. 

"At dawn, the farm workers will march from the countryside to Foggia, in order to claim dignified working conditions," he said.

The International Organization for Migration commented that despite efforts by institutions and civil society to fight against exploitation, "each summer we find ourselves needing to comment on the death of Italian and foreign workers in the agri-food sector."

The archbishop of Foggia, Vincenzo Pelvi, also weighed in on the accidents saying "we must not, we cannot remain indifferent before the tragic deaths of our brothers."

He called for a mass to be held Monday evening at the cathedral to pray for the 16 victims of the two accidents and for the recovery of the injured.