The tear gas used on migrants at the U.S.-Mexico border at the weekend, which prompted criticism of President Trump, was also used almost 80 times under the Obama administration, according to Homeland Security data.

Critics of Trump had denounced the action by federal agents as overkill when they used the tear gas to repel a crowd of migrants that included angry rock-throwers and barefoot, crying children.

But figures from the Department of Homeland Security, which emerged on Tuesday, show that the same gas was used more than once a month during the later years of Obama's administration.

Critics of Trump had denounced the action by federal agents as overkill when they used the tear gas to repel a crowd of migrants that included angry rock-throwers and barefoot, crying children on Sunday at the San Diego-Tijuana border crossing

That tear gas, known as 2-chlorobenzylidene malononitrile, was used by U.S. Customs and Border Protection agents a total of 126 times since 2010.

The chemical was used at the border 26 times in 2012, 27 times in 2013, 15 times in 2014 and eight times in 2015.

The data doesn't provide details of each incident, including the locations or size of the groups targeted.

There is barely any footage or photos of the tear gas being deployed under the Obama administration.

Trump faced backlash after photos emerged of migrants being targeted at the border, including a woman and two young children running from the tear gas.

He kept to a hard line when defending its use at the San Diego-Tijuana border crossing on Sunday.

'They were being rushed by some very tough people and they used tear gas,' Trump said Monday of the previous day's encounter.

'Here's the bottom line: Nobody is coming into our country unless they come in legally.'

Migrants run from tear gas launched by U.S. agents at the Mexico-U.S. border on Sunday. The same tear gas was used dozens of times under the Obama administration

Trump faced backlash after photos emerged of migrants being targeted at the border, including a woman and two young children running from the tear gas

At a roundtable in Mississippi later Monday, Trump seemed to acknowledge that children were affected.

'Why is a parent running up into an area where they know the tear gas is forming and it's going to be formed and they were running up with a child?' the president asked.

He said it was 'a very minor form of the tear gas itself' that he was assured was 'very safe.'

Without offering evidence, Trump claimed some of the women in Sunday's confrontation are not parents but are instead 'grabbers' who steal children so they have a better chance of being granted asylum in the U.S.

The showdown at the border crossing has thrown into sharp relief two competing narratives about the caravan of migrants who hope to apply for asylum but have gotten stuck on the Mexico side of the border.

Trump portrays them as a threat to U.S. national security, intent on exploiting America's asylum law but others insist he is exaggerating to stoke fears and achieve his political goals.

The U.S. military said Monday that about 300 troops who had been deployed in south Texas and Arizona as part of a border security mission have been moved to California for similar work.

The military's role is limited largely to erecting barriers along the border and providing transportation and logistical support to Customs and Border Protection.

A Honduran migrant lies on the riverbank as Mexican police move away from tear gas fired by U.S. agents at the Mexico-U.S. border in Tijuana, Mexico on Sunday

Democratic lawmakers and immigrant rights groups blasted the tactics of border agents.

'These children are barefoot. In diapers. Choking on tear gas,' California Gov.-elect Gavin Newsom tweeted. 'Women and children who left their lives behind - seeking peace and asylum - were met with violence and fear. That's not my America.'

U.S. Customs and Border Protection Commissioner Kevin McAleenan said the administration's concerns about the caravan 'were borne out and on full display' Sunday.

McAleenan said hundreds - perhaps more than 1,000 - people attempted to rush vehicle lanes at the San Ysidro crossing. Mexican authorities estimated the crowd at 500. The chaos followed what began as a peaceful march to appeal for the U.S. to speed processing of asylum claims.

McAleenan said four agents were struck with rocks but were not injured because they were wearing protective gear.

Border Patrol agents launched pepper spray balls in addition to tear gas in what officials said were on-the-spot decisions made by agents. U.S. troops deployed to the border on Trump's orders were not involved in the operation.

'The agents on scene, in their professional judgment, made the decision to address those assaults using less lethal devices,' McAleenan told reporters.

The scene was reminiscent of the 1980s and early 1990s, when large groups of migrants rushed vehicle lanes at San Ysidro and overwhelmed Border Patrol agents in nearby streets and fields.