US border guards have used tear gas against a group of migrants attempting to storm the US border with Mexico.
Video footage shows dozens of people running towards the fence that separates the two countries near the city of Tijuana, while photos show clouds of tear gas rising into the air.
The US has also closed the border crossing to vehicles and pedestrians.
Tensions have been high in the Mexican city since the arrival of thousands of migrants earlier this month.
The migrants – including many women and children – are in Tijuana after travelling more than 4,000km (2,500 miles) from Central America.
They say they are fleeing persecution, poverty and violence in their home countries of Honduras, Guatemala and El Salvador.
However, they now face a long wait to see if their asylum applications will be accepted by the US, with President Donald Trump vowing to keep each migrant on the Mexican side of the border until courts have decided their case. This could take months.
Amid growing desperation on Sunday, a group of about 500 migrants – who had been taking part in a peaceful protest demanding to be allowed to cross – made a run for the border.
According to news agency AFP, a number managed to climb over a first fence. It was as they tried to cross a second, spike-topped wall that officials on the US side began throwing tear gas.
An AFP journalist saw the migrants – including mothers and children – trying to protect themselves from the gas, with some crying out that they only wanted to find a work and a better life in the US.
Honduran migrant Ana Zuniga, 23, tried to cross with her three-year-old. She told AP: “We ran but when you run the smoke smothers you more.”
Mr Trump threatened to close the entire US-Mexico border earlier this week if it was felt the US was going to “lose control” of the situation.
He also said he had given troops at the border the go-ahead to use lethal force if needed.
Mr Trump has deployed about 5,800 troops to the border. He previously described the migrants as an “invasion”.
Migrant caravan: US fires tear gas at Mexico border