Mexican police have briefly scuffled with some of the 1,600 Central American migrants who are confined to an improvised shelter in the border town of Piedras Negras.

Video of Wednesday's incident show some migrants tearing down a temporary awning and trying to wrestle metal barricades away from police.

The government of the border state of Coahuila says the migrants were angry about not being allowed out to go to a local store. It says about 30 were later permitted to go.

The state government says some of the migrants have asked to be taken to other cities in northern Mexico, presumably thinking they would have more freedom of movement.

There is a heavy police and military guard around the improvised shelter at an old factory complex.