Dozens of migrants travelling in a caravan to seek asylum in the US have been stopped at the border.

US border officials told some 150 people, many travelling with children, that the Mexico-US border crossing near San Diego was already full.

It was not immediately known whether the migrants from Central America would be allowed in later or turned back but the group appears to be staying put.

President Donald Trump says the caravan is a threat to the safety of the US.

The group has been a frequent target for the US president, who has argued in his tweets that it showed the need to tighten immigration laws.

He has asked states bordering Mexico to send troops to shore up security until his proposed border wall is built.

The caravan set off for the US on 25 March in southern Mexico, near the Guatemala border and at one point numbered more than 1,000 people.

The group travelled by bus, train and on foot during its 3,200km trek to the US border, with many saying they were fleeing persecution and violence in their home countries.

Read more on BBC.