Migrant caravan: Trump announces stones thrown will be treated as firearms while travelling immigrants head to US border

Thousands of refugees and migrants from Central America are walking and hitchhiking northwards through Mexico, and Donald Trump has dispatched more than 5,000 troops southwards to help secure the US border amid what has has termed “an emergency”.

In addition to this original group, more than 1,000 migrants in a second caravan that forced its way across the river from Guatemala have begun arriving in the southern Mexico city of Tapachula.

About 2,000 migrants began walking north from El Salvador's capital on Wednesday, making it the third group to try and reach the US.

Mr Trump made clear Thursday he will do everything in his power to stop them, dispatching extra troops, threatening to shut border entirely and saying in an afternoon press conference the military would consider rocks thrown at active troops "firearms".