Thousands of migrants travelling in a mass caravan have burst through a Guatemalan border fence and streamed towards Mexican territory, defying Mexican authorities' entreaties for an orderly crossing and US President Donald Trump's threats of retaliation.

Key points: Central American migrants clash with Mexican and Guatemalan border police

Central American migrants clash with Mexican and Guatemalan border police Mexico says those with proper paperwork will be allowed to enter country

Mexico says those with proper paperwork will be allowed to enter country US authorities struggling to deal with number of Central American migrants crossing into Arizona

As the migrants surged across the border bridge a group of around 50 managed to force their way through before being met by police in riot gear, who subdued them with pepper spray, before others retreated, with some jumping to the river below.

Many with small children were seen queuing in order to register with Mexican immigration authorities, while on the Guatemalan side of the border dozens were left stranded, unable to get past Guatemalan police who stood guard in front of metal gates.

The refugees were met by Mexican Federal Police in riot gear. ( AP Photo: Moises Castillo )

Luis Manuel Lopez Moreno, Mexico's ambassador to Guatemala asserted those with the proper paperwork would be allowed to make the move into Mexico.

"We respect the freedom of movement of immigrants and above all, based on Mexican immigration law, we are receiving people who are choosing to submit to immigration in order to submit an application for refugee or a humanitarian visa, depending on the case," Mr Moreno said.

Meanwhile in Arizona large groups of Central American migrants continue to surrender to Border Patrol agents, with the arrival of one recent group numbering 108 captured in dramatic video images, authorities said on Friday.

The agency said camera operators monitoring movement on Thursday afternoon along the US-Mexico border in the Yuma area captured images of a large number of people being dropped over the border wall east of the San Luis Port of Entry.

It said the smugglers never crossed the border while they helped migrants over the wall in four places. The group was comprised of 100 Guatemalans and eight Hondurans. They included 52 children, nine of them 5 years old or younger.

Children were carried over the border fence as thousands of migrants rushed towards Mexico. ( AP Photo: Oliver de Ros )

US Immigration and Customs Enforcement in Arizona earlier this month began releasing hundreds of people to await court dates, saying it did not have the capacity to hold an "incredibly high volume" of migrant families showing up at the border.

"Coordinated smuggling of large numbers of Central Americans is taking place daily here," Yuma Sector Chief Patrol Agent Anthony Porvaznik said in a written statement.

While Mexican men travelling without relatives once made up the bulk of the migrants, Guatemalans and other Central Americans travelling in families or as unaccompanied minors are now the norm.

Migrants tired of waiting to cross into Mexico jumped from a border bridge into the Suchiate River in Tecun Uman, Guatemala. ( AP Photo: Oliver de Ros )

After meeting with Mexican President Enrique Pena Nieto, US Secretary of State Mike Pompeo said Mexican police officers had been injured trying to stop the caravan, before accusing the caravan of using women and children as shields.

He said four policeman had been injured in the clashes on the border.

"That's evidence of what this really is: this is a large group of people, they are putting women and children in front of this caravan to use as shields as they make their way through. This is an organised effort to come through and violate the sovereignty of Mexico."

Earlier, the numbers trying to enter the United States had prompted a warning from Mr Trump, where he insisted he would call up the US military and close the southern border with Mexico if Mexico failed to stop the masses of people from travelling through that country.

"We have a very good relationship with Mexico. I said look we have lousy laws. I hope you're not going to let these people come through your country and march a thousand miles up through your country and come through our borders, because our laws are horrendous," Mr Trump said.

"We are about law and order and borders and jobs, and they are about allowing crime to enter our country with open borders.

"Because many of those people, a percentage, a fairly big percentage of those people are criminals and they want to come into our country and they're criminals. And it's not happening on my watch, not going to happen.

"So as of this moment, I thank Mexico. I hope they continue, but as of this moment I thank Mexico.

"If that doesn't work out, we're calling up the military, not the guard, we are calling up the military and we're going to have the military stationed there, not coming into this country. They might as well turn back. They're not coming into this country."

AP