Mexico has dispatched two Boeing 727s full of federal police officers to its southern border, as the country prepares for the arrival of a migrant caravan of thousands from Central America.

Five hundred federal police officers in riot gear arrived on Wednesday in Tapachula, Chiapas on the border with Guatemala, where some 4,000 migrants are now marching northward.

The presence of federal forces on the southern border of the country is not to stop migrants from crossing the border, but to help immigration officials maintain order, Mexican Federal Police Commissioner Manelich Castilla Craviotto told Noticeros Televisia.