US Customs and Border Protection announces traffic at the San Ysidro port of entry has been suspended.

San Diego, California – US Customs and Border Protection temporarily closed all vehicle and pedestrian traffic at the major San Ysidro port of entry between Tijuana, Mexico and San Diego, California on Sunday.

The agency made the announcement as hundreds of migrants and refugees marched towards the border in an attempt to put pressure on the US government to allow thousands of asylum seekers to enter the United States.

According to several journalists in Tijuana, US authorities used tear gas on migrants and refugees, including children, who approached the border fence near the El Chaparral crossing. A small group breached the border, local media reported.

“To prepare for the possibility that additional groups would also break off from demonstrations for a possible attempt or attempts to rush illegally through the port of entry, CBP suspended operations at the port of entry,” the agency said in a statement.

The port of entry remained closed for about six hours before being re-opened.

The developments on Sunday come as frustration grows in Tijuana over the slow processing of asylum claims by US authorities.

Thousands of migrants and refugees have arrived in the Mexican border city in recent weeks as part of a caravan, dubbed the Central American exodus. Many have told Al Jazeera they are fleeing violence, poverty or political persecution.

More than 5,000 migrants and refugees have been cramped into a Tijuana stadium complex that is more than 2,000 people over capacity. Rights groups have accused to the US government of stalling the processing of asylum claims, allegations CBP denies.

Aerial view of Central American migrants and refugees being stopped by federal police officers near El Chaparral port of entry in the US-Mexico border [Pedro Pardo/AFP]

US President Donald Trump has sought to sow fear over the collective exodus by deploying thousands of US military troops to the border and giving them expanded powers, including the “ok” to use lethal force.

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The Trump administration also implemented new asylum rules, which have been temporarily blocked by a federal court. Under the new rules, individuals crossing the border between official ports of entry would not be eligible for asylum. A judge last week blocked the rules from being enforced pending further hearings.

‘Immigrants are welcome’

Prior to the border closure, hundreds gathered in San Diego to march in solidarity with the migrants and refugees in Tijuana.

The group, which included a collection of different rights organisations, accused the Trump administration of creating a “war-like atmosphere” against the Central American exodus in Mexico.

Holding banners that read “immigrants are welcome” and “money for jobs, not walls”, more than 200 people marched towards the San Ysidro port of entry.

“As a mother, I understand that families have to be together,” said 37-year-old Kelly Leon, who attended the march with her family.

“For me, it’s clear that you don’t just travel thousands of miles with your whole family, unless there is something that you [are really running] away from,” she told Al Jazeera.

San Diegans protesting at the border in solidarity with the Central American asylum seekers in Tijuana: pic.twitter.com/aGoNOntDxD — Jurriaan van Eerten (@JurriaanvEerten) November 25, 2018

While Leon grew up in the US, her husband, 40-year-old Armando Leon, was brought by his parents from Mexico when he was a child.

“I think the majority of people in San Diego stand in solidarity with these migrants, that’s what we hear around us,” Kelly Leon told Al Jazeera. “Especially from people who have families themselves.”

Protesters supporting the migrants and refugees in Tijuana, Mexico show their solidarity during a march next to the border wall with Mexico in the San Ysidro neighbourhood of San Diego [Mike Blake/Reuters]

Among the groups present at Sunday’s march was Veterans for Peace.

Paul Ross, 74, who served in the Vietnam War, said he felt compelled to come to the border and make his voice heard.

“Latin America has had one dictator after the other,” Ross told Al Jazeera. “Almost all of which have had support from the United States, in the beginning, to work towards regime change. The poverty and problems they have there now, have a history which we have to understand.”

While holding a flag with Veterans for Peace written on it in combination with a logo with a flying dove, Ross told Al Jazeera he believed the current exodus of Central Americans is a result of the involvement of the US in affairs in these countries.

“Now these places have become very dangerous and problematic, so the people have no place to go any more. They have no choice.”

Other marches in support of migrants and refugees were planned across the US.