
The first wave of the migrant caravan has hit the US border, with a group of about 50 seeking asylum at the Tijuana crossing into California.

The group of 50 Central American migrants who set out from southern Mexico in late March arrived in Tijuana, Mexico on Wednesday, after splintering off from the original caravan of 1,500.

'Since yesterday, some began to cross into the United States to turn themselves in from Tijuana and request asylum. We understand more of (the migrants) will do the same,' said Jose Maria Garcia, director of Juventud 2000, an organization dedicated to assisting migrants.

He said more migrants, many of whom are stranded in Mexico's central states, are expected to arrive in the coming days.

The splinter groups headed toward the US have been undeterred by President Donald Trump's threat to deploy the National Guard along the border, after Trump called California's contribution to the mission a 'charade'.

A Central American migrant from the caravan is seen as a group of 500 migrants arrives in Hermosillo, Sonora state on Saturday. Another splinter group of about 50 members from the caravan has already arrived in Tijuana to claim asylum

Central American migrants ride a northern-bound train known as 'La Bestia,' or The Beast, as they arrive to Hermosillo

Central American migrants ride a northern-bound train known as 'La Bestia,' or The Beast, in Hermisillio on Saturday

A migrant from El Salvador jumps off the northern-bound train known as 'La Bestia,' in Hermosillo, Sonora state on Saturday

Central American migrants from the caravan rest at a community shelter after arriving by train to Hermosillo, Sonora state, Mexico on Saturday. They hope to reach the US by Tuesday

Honduran migrants from the caravan pose for photos with their national flag on Saturday as they make their way to the US

A US Border Patrol agent walks near the secondary fence separating Tijuana, Mexico and San Diego in this file photo

'We will continue to receive them and it will be up to them if they stay in the country or leave,' Garcia said.

Many of the migrants seeking asylum will likely claim they are fleeing gang violence in their home countries. Honduras, El Salvador and Guatemala are among the most violent and impoverished countries in the Americas.

Migrants claiming asylum, in particular those traveling with children, are typically released into the US after they are processed, and told to appear in court to support their asylum claim.

Critics say the process offers a loophole for entry into the US and that bogus asylum seekers will simply disappear after they are released. Immigrant advocates believe the vast majority of asylum seekers have legitimate claims, however.

Meanwhile, another group of about 500 caravan members has jumped a freight train headed north toward the border.

They were last spotted on Saturday in Hermisillo, Sonora state, about 175 miles south of the crossing at Nogales, Arizona.

The group riding the freight trains north hope to reach the US border by Tuesday. Freight lines from Hermisillo run both to Nogales and to Mexicali, on the border with California.

Nicaraguan migrant Jesus Emmanuel Diaz Rubio eats a sandwich after getting off 'La Bestia' on Saturday

Central American migrants, moving in a caravan through Mexico, rest in Mazatlan, in Sinaloa state, Mexico on Saturday

A Central American migrant,rests at a community shelter after arriving by train to Hermosillo, Mexico on Saturday

Earlier in the week, they were seen in Guanajuato state stretching out on the roofs of freight cars as they made for the border.

One of the migrants is Honduran Mirna Ruiz. He said: 'We are heading north seeking a better life.'

'As you know, in Honduras we just can't live there anymore because of the gangs. We can't even go shopping because we are afraid.

'We are also worried that our children will be recruited by the gangs. Those are the fears in our country.'

Since peaking at around 1,500 people, the so-called migrant 'caravan' has dwindled under pressure from Trump and Mexican migration authorities, who vowed to separate those migrants with a right to stay in Mexico from those who did not.

In Mexico City, Organizer Irineo Mujica had said the capital was the caravan's last official stop, but many of the migrants feared going solo on the dangerous final leg north and decided to keep travelling en masse.

Some who had split off to press on alone reported back about kidnappings and having their papers for safe passage torn up.

The caravan is an annual, symbolic event held around Easter each year to raise awareness about the plight of migrants. It historically does not go all the way to the border and that was not the original plan this year, Mujica said.