Twelve African farm labourers have died in a head-on collision between a van and a lorry near Lesina in the Foggia region of southern Italy.
The labourers were returning from the fields, packed into a van which had Bulgarian number plates.
Three other people were injured in the crash, including the lorry driver.
Four migrant farm workers died in a similar crash in the same region on Saturday. Many seasonal workers hired by gangs in Italy get very meagre pay.
After Saturday's crash a union of farm labourers announced a strike for Wednesday, with a "red hat" march to Foggia - a mark of solidarity with the four who died. The red hats symbolise the hats worn by tomato pickers in the fields around Foggia.
Their pay is as low as one euro for picking 100kg (221lb) of tomatoes.
Conditions are very precarious for thousands of African migrants in Italy, where the populist government is trying to stop people-smuggling gangs sending more boatloads from Libya.
The boats are perilously overcrowded and more than 1,500 people have drowned crossing the Mediterranean this year, the UN refugee agency says.
More than 650,000 migrants - mostly from sub-Saharan Africa - have come ashore in Italy since 2014, stretching resources in regions already struggling with high unemployment.