After US President Donald Trump vowed that asylum seekers would not easily enter the country, authorities shut the country's largest border and fired tear gas at approaching migrants.
Traffic was suspended for several hours at the San Ysidro port of entry between San Diego and Tijuana.
When several hundreds of migrants tried to breach a fence from the Mexican city of Tijuana, US border officers began firing tear gas at them. Hundreds made it over the first barrier and were trying to cross a second which was topped with spikes. US Army helicopters flew low overhead according to reports.
Authorities said that they had temporarily closed the San Ysidro crossing point—one of the busiest between the two countries—to both vehicular and pedestrian traffic.
The dramatic shutdown took place only three days after Trump threatened to close the "whole border" with Mexico if "it gets to a level where we are going to lose control or people are going to start getting hurt."
The order close the border was lifted after some hours.
Mexican Interior Minister Alfonso Navarrete accused some of the migrants of attempting the Tijuana crossing in a "violent way".
"We are going to act and proceed to their deportation," he told the Milenio television network, adding: "Far from helping the caravan, they are hurting it."
Video clips posted on Twitter showed large numbers of migrants dashing across a shallow concrete waterway toward the border. Several thousand migrants, mostly from Central America, have been gathering in Tijuana in hopes of entering the US.
Secretary of the US Department of Homeland Security (DHS) Kirstjen Nielsen later issued a statement accusing the migrants of seeking to harm border patrol personnel "by throwing projectiles at them".
"As I have continually stated, DHS will not tolerate this type of lawlessness and will not hesitate to shut down ports of entry for security and public safety reasons," she said, adding the US would "seek to prosecute" offenders.
At least 500 migrants, including women and children, had been taking part in a peaceful demonstration in Tijuana before dashing toward the border in an attempt to clamber over a first metal barrier there.
"Are we in the United States yet?" some asked in desperate tones.
The migrants tried to protect themselves—covering their faces, with mothers holding their children close. There were cries of pain, desperation and frustration as the crowd swirled over the border line and back.
Some migrants shouted that they only wanted to make their way to a better life. But amid the stinging gas, several migrants turned back.
