The main truckers union in the Dominican Republic on Monday blocked transport of all freight through border crossings into neighboring Haiti, citing concerns about their safety.

The Dominican truckers said they were protesting recent violence against them while in Haiti. They asserted that some 60 trucks were pelted with rocks in recent days and some were looted.

Union leader Blas Peralta said the blockade will continue until Haiti provides better security on its side of the border. For now, Dominican trucks are being unloaded at the border crossings and Haitian buyers must arrange transport for goods.

Normally, some 200 trucks each day carry tons of food, construction materials and other items across the border on the island of Hispaniola, which is shared by the two countries. Haiti is the Dominican Republic's biggest export market after the United States.

It's the second protest so far this year by Dominican truckers. In March, they refused to cross the border for several days amid protests in Haiti about the treatment of Haitian citizens in the Dominican Republic.

The truckers' latest protest comes as the Dominican Republic is under international scrutiny for immigration policies that affect mostly Haitians and people of Haitian descent.

There was a June 17 deadline for migrants to apply for legal residency under a controversial program aimed at regulating the flow of migrants across the porous border with Haiti. Authorities have warned that anyone without proof of legal residency faces deportation.

Haitian Prime Minister Evans Paul has warned that deportations into Haiti could create a "humanitarian crisis."