Salvadoran migrant Tania Avalos sits next to firefighters during a search for her husband Oscar Alberto Martinez Ramirez and her daughter Valeria, who were dragged by a current at the Rio Bravo river while trying to reach the U.S. Picture: Alejandro Hernandez/Expreso de Matamoros via Reuters

Mexico City - The Salvadoran embassy in Mexico will on Thursday repatriate the bodies of a Salvadoran father and his small daughter who drowned when trying to cross a river straddling the US-Mexican border, the Mexican newspaper La Jornada reported.

A photo of the bodies of Oscar Alberto Martinez, 26, and 23-month-old Valeria, lying face down in shallow water with her arm draped around his neck, sparked global outrage over the difficulties migrants face.

Their remains will be taken to Monterrey in Mexico and then flown to El Salvador, La Jornada said.

However, Martinez' widow Tania Avalos may decide to cremate the bodies and throw the ashes into the Rio Grande river, to leave them near their unattained destination - the United States, the Mexican newspaper El Grafico reported.

Martinez, Avalos and Valeria arrived in Mexico more than two months ago and were given humanitarian visas, according to Mexican and Salvadoran media.

But they were worried that US President Donald Trump's crackdown on migration would prevent them from crossing the border into the US, the news website ElSalvador.com quoted their relatives as saying.

Tania Vanessa Avalos, accompanied by her cousin Milton, shields her face from the press as she walks between government offices in Matamoros, Tamaulipas state, Mexico. Picture: Rebecca Blackwell/AP

The migratory formalities also turned out to be long and complicated, and the couple started running out of money, El Grafico quoted Avalos as saying.

"Therefore on Sunday, Oscar said we should already cross the river, that I should trust and have faith that nothing would happen. He took Valeria in his arms and we entered, hanging onto a rope, but the waters started pulling us away.

"Oscar held the girl up with one arm, but he could not resist and she was let loose. I managed to get back to the shore, but I saw how the water pulled my husband and my daughter away."

Avalos alerted the security forces, who found the bodies 12 hours later.

Oscar wanted to migrate to find work and to "give our daughter, Valeria, a better life," the widow said, drying her tears.

Oscar's mother, Rosa Ramirez, told the Salvadoran newspaper La Prensa Grafica that she had warned him against the dangerous journey. But the couple wanted to work in the US to be able to buy their own home in El Salvador, and "they therefore opted for the American dream," Ramirez said.

"Mom, I love you," were Oscar's last words to his mother from Mexico. "Take care, we are well over here."

Other dramatic images of migrants were meanwhile made public. A video, published by the Mexican newspaper El Universal, showed a Haitian woman at a migrants' reception centre near Mexico's border with Guatemala.

She is lying on the ground, weeping and talking through an opening underneath what looks like a metal gate.

The woman says there is no drinking water, hardly any food and that her son is ill. "Help me, justice," she she shouts, again and again.

Amnesty International on Wednesday blamed Martinez' and Valeria's death on US migration policies.

"If you are horrified by the tragic images from the Rio Grande and the recent deaths of migrants in the desert, you are not alone. These deaths are the result of Trump Admin policies that deny families their legal right to seek asylum and force them into desperate circumstances," the rights group tweeted.

Trump commented on the impact of the photograph before leaving for the G20 summit in Japan. He blamed Democrats in Congress for not changing US laws so that people will not take such risks.

"If we had the right laws - that Democrats aren't letting us have - those people wouldn't be trying," he said, speaking outside the White House.

Beyond drowning, Trump said other things are happening to people, including women being raped.

"If they fix the laws, they wouldn't have that," Trump said. "That journey across that river is a very dangerous journey."

Trump also said that humanitarian aid bills to help the children at the border are currently in the House and Senate. He said he had spoken with congressional leaders and believes the two sides would come together and produce a bipartisan bill.

The picture of the two bodies evoked comparisons with the 2015 picture of Alan Kurdi, a 3-year-old Syrian boy whose body washed up on the Turkish shore. The image shocked the world and became a symbol of the global migrant crisis.

"Less than four years after [Kurdi's death], we are once again confronted with powerful visual evidence of people dying during their dangerous journeys across borders," the head of UN Refugee Agency UNHCR, Filippo Grandi, said in a Wednesday statement.

The bodies of El Salvadoran migrant Oscar Alberto Martinez Ramirez, 25, and his nearly two-year-old daughter Valeria, are placed into a funeral home van at the morgue in Matamoros, Tamaulipas state, Mexico. Picture: Rebecca Blackwell/AP

Pope Francis said he had seen the picture of the two bodies with "immense sadness."

"The Pope is profoundly saddened by their death, and is praying for them and for all migrants who have lost their lives while seeking to flee war and misery," the Vatican statement added.

"One day we will manage to build a country where migration will be an option and not an obligation. Meanwhile, we will do what is possible. God help us," Salvadoran President Nayib Bukele said on Tuesday.

Hundreds of thousands of people leave El Salvador, Honduras and Guatemala every year to flee crime-related violence and poverty. But Rosa Ramirez said she hopes that Salvadorans will now not "even think of" migrating.

The Mexican city of Ciudad Juarez, which lies on the Rio Grande, meanwhile published a video warning migrants against trying to cross the river.

"Migrant friend, do not allow the search for your dreams to turn into a nightmare," the video said.

"Without life, there is no future nor a dream to reach."

dpa