By Julia Love and Lizbeth Diaz
MEXICO CITY (Reuters) - Mexican leader Andres Manuel Lopez Obrador faces growing criticism he is doing U.S. President Donald Trump's bidding after erecting a "wall" of security forces who clashed with Central American migrants near the Guatemala border this week.
Mexico, under the threat of punitive U.S. tariffs, has bowed to Trump's demands to contain mass movements of migrants traveling through the country toward the U.S. border.
Such concessions previously stirred little criticism from the Mexican public, due to president Lopez Obrador's reputation as a leftist supportive of the poor and foreign migrants.
But footage of Mexico's National Guard military police marching into Central Americans and using tear gas has triggered growing condemnation, including from the United Nations.
"It's a wall of riot shields," said Duncan Wood, director of the Wilson Center's Mexico Institute in Washington. "I didn't think I would live to see the day when Mexico would do this kind of thing."
Lopez Obrador defended the National Guard and migration officials at his regular news conference. He said the caravan of Central American migrants was not spontaneous, hinting that Honduran activists were driving it for political ends.
Previous Mexican governments have also faced criticism they were bending to Washington's will on migration.
Trump has made immigration a key issue in his re-election campaign and wants a wall built along the U.S-Mexico border.
Foreign Ministry spokesman Roberto Velasco rejected the notion that his government had effectively created Trump's wall along the Suchiate River separating Mexico and Guatemala.
"That's totally wrong," he said in response to a question on Mexican radio. "Unfortunately, Mexico has never developed a border, which means we inherited poor infrastructure."
Mexican offices of several U.N. agencies said they were worried about the impact Thursday's operations would have on children and other "vulnerable" groups.
"Mexico has the right to control the entry of foreigners as long as there is no excessive use of force," the groups wrote in a joint statement, urging Mexico not to separate families.
On Thursday, National Guard members corralled families onto buses for detention and deportation.
Enrique Vidal of human rights group Fray Matias de Cordova, who witnessed the scenes, said National Guard members began clashes by marching on the migrants. Some migrants were beaten, while pepper spray affected pregnant women, children and people with disabilities, and one minor passed out, he added.
As Mexico put migrants into detention centers on Monday, Fray Matias recorded three cases of children separated from their parents from a few hours to up to two days, Vidal said.
He said Fray Matias and other rights groups have been stopped from visiting detention centers to monitor conditions, or have had to conduct interviews with security forces present.
Lopez Obrador has offered migrants jobs. But Vidal said that when they reached the southern border, migrants found "a military operation of containment and detention."
Under pressure from Trump, Mexico has deployed thousands of National Guard to stem migrant flows. Apprehensions at the U.S.-Mexico border have fallen about 70 percent over seven months.
However, Mexico's response has pushed migrants to take more dangerous routes, said Christopher Gascon, head of the U.N.'s International Organization for Migration's (IOM) Mexico mission.
"They put themselves in even riskier situations," he told Reuters.
As of Thursday, Mexico said it had transferred at least 800 migrants, including unaccompanied minors, to migration centers where they would be given food, medical attention and shelter.
Thousands of migrants have entered Guatemala from Honduras in recent days, one of the biggest surges since three Central American governments signed agreements with Washington obliging them to take on more of the burden of dealing with migrants.