Thousands of migrants march out of city in Mexico towards US border

Migrants, most from Central America, depart the town of Tapachula, Mexico (Edgar H Clemente/AP)

More than 2,000 migrants, mainly from Central America, have walked out of a city in southern Mexico where they have essentially been trapped.

The migrants walked along a major road leading west and north towards the US border, and pushed past a line of state police who were trying to stop them.