The UN human rights agency on Tuesday voiced concern at the United States' deportation of migrants back to Haiti, saying that people massed along the border who feared violence or persecution at home had a right to seek asylum. "We are disturbed by the images that we have seen and by the fact that we have seen all these migrants and refugees and asylum-seekers in transport to Port-au-Prince," UN human rights spokesperson Marta Hurtado told a briefing in Geneva. "We are seriously concerned by the fact that it appears there have not been any individual assessments of the cases ... and that therefore maybe some of these people have not received the protection that they needed." A camp under a bridge over the Rio Grande on the border between Mexico and Texas has become the latest flashpoint for US authorities seeking to stem a flow of migrants fleeing extreme violence or poverty in their home countries. The United States has started flying migrants out of a Texas border town that has seen an influx of mostly Haitian migrants over the past week. Three flights landed at Haiti's Port-au-Prince airport on Sunday, each carrying 145 people, the Associated Press reported. Social media images which appear to show border agents on horseback driving migrants back to a river like cattle have sparked an investigation in the US. The pictures widely shared on social media show the riders using their reins against the migrants and pushing them back towards the Rio Grande in Texas. Homeland Security Secretary Alejandro Mayorkas says his department will investigate reports of alleged abuse. He said the officers were trying to manage the migrants crossing the river. Some 13,000 mainly Haitian migrants have gathered in a makeshift camp under a bridge connecting Del Rio to Mexico's Ciudad Acuña on the US-Mexico border. White House spokeswoman Jen Psaki said the footage was horrible to watch. The first flights carrying migrants from the Del Rio camp arrived in Haiti on Sunday with at least three more due to make the journey on Monday, according to the flight tracking website Flightaware. "While some people arriving at the border may not be refugees, anyone who ... claims to have a well-founded fear of being persecuted in their country of origin - they should have access to asylum and to have their claim assessed before being subjected to expulsion or deportation," U.N. refugee agency spokesperson Shabia Mantoo told the briefing. The United States is expelling migrants under an order issued in March 2020 by the US Centers for Disease Control and Prevention, which cited the need to limit the spread of the coronavirus.-- Agencies