Mexican President Andres Manuel Lopez Obrador urged the United States on Wednesday to act quickly to tackle the causes of the migrant crisis affecting the two neighboring countries.

"Enough talking, it's time to act," Lopez Obrador told reporters as thousands of Haitian and other migrants massed on Mexico's northern border seeking access into the US.

Mexico and Central American countries were still waiting for several billion dollars pledged by Washington for economic development to reduce the need for migrants to flee poverty, he said.

"There was a commitment that they were going to invest $4 billion-$2 billion for Central America and $2 billion for Mexico. Nothing has come－nothing," Lopez Obrador said.

The president said US administrations had invested little in recent decades in the development of Latin America, action that could reduce migration flows. The migration problem should not be solved with force, he said, but with productive options that discourage emigration.

His government said people-smuggling crimes in Mexico this year have more than tripled from levels in 2020, as Mexico battles to cope with a sharp increase in illegal immigration at the US border.

Between January and August, Mexico registered 1,232 people-smuggling crimes, a jump of nearly 228 percent from the 376 logged during the same period in 2020, Security Minister Rosa Icela Rodriguez told a news conference.

It came as the political situation involving Haitian migrants at the border in Texas intensified, with one report saying thousands of the asylum-seekers have been released into the country despite the administration of President Joe Biden saying they would be placed on repatriation flights.

Two US officials told The Associated Press of the migrants' release into the US interior, undercutting the Biden administration's public statements that the thousands in one camp faced immediate expulsion.

'Very, very large scale'

Haitians have been freed on a "very, very large scale" in recent days, according to one US official who put the figure in the thousands, the news agency reported. Haiti has been hit by recent political turmoil and natural disasters.

The Daily Mail of London, citing a source, said that just over 1,000 of the nearly 15,000 migrants who camped under a bridge in Del Rio, Texas, across from Mexico have been flown back to Haiti.

The border chaos also has renewed the political dispute surrounding illegal immigration in the US, with Republican Texas Governor Greg Abbott sending a convoy of state vehicles to serve as a steel barrier at the Mexican border, while Democrats in Washington have condemned what they called mistreatment of migrants by US Customs and Border Patrol, or CBP, agents.

The releases came amid a quick effort to empty the camp under the bridge that, according to some estimates, held more than 14,000 people over the weekend in a town of 35,000.

The White House is facing sharp bipartisan condemnation. Republicans say Biden administration policies led Haitians to believe they would get asylum. Democrats are expressing outrage this week after images appeared of Border Patrol agents on horseback using aggressive tactics against the migrants. The images went viral on social media.

During a news conference on Wednesday, White House press secretary Jen Psaki said Border Patrol agents used "brutal" methods against migrants crossing the Rio Grande River into Texas.

Psaki said officials had watched "horrific video of the CBP officers on horses using brutal and inappropriate measures against innocent people". Psaki noted that there is an independent investigation of the incident under way, and that officers involved "were placed on administrative leave and will not be interacting with any migrants".

The images showed Border Patrol agents using their horse reins to keep migrants away. Critics have charged that the reins were used in a whip-like fashion.

Heng Weili in New York, agencies and Xinhua contributed to this story.