Donald Trump has conceded that “probably more has to be done” after two mass shootings left 29 people dead in the US.
The US president said “we’re going to take care of it” after the attacks in Texas and Ohio happened within a few hours of each other.
Facing accusations that he has encouraged “white nationalism” and stoked anti-immigrant sentiment, the US president added that “hate has no place in our country”.
Suspect Patrick Crusius, 21, was arrested after 20 people were killed at a Walmart supermarket in the Texan city of El Paso, which has a large Hispanic population.
Several hours later, a gunman shot dead nine outside a bar in Dayton, Ohio, before being killed by police within a minute.
The president said the gunmen were “really very seriously mentally ill”, adding that shootings have been happening “for years and years” and “we have to get it stopped”.
Authorities said the supermarket rampage in Texas appeared to be a racially motivated hate crime and federal prosecutors were treating it as a case of domestic terrorism.
Officials are investigating a “hate-filled” online post they believe was published by the gunman.
The four-page document, which was posted online, appears to describe the gunman’s motives for the attack, and expresses extreme anti-immigrant and racist views, particularly against the Hispanic population.
Crusius could face the death penalty if convicted over the massacre in El Paso, where police first received reports of gunfire on Saturday at 10.39am local time (4.39pm BST).
At 1am local time (6am BST) on Sunday, 24-year-old Connor Betts opened fire in Dayton, Ohio. His 22-year-old sister Megan was among those killed in the attack – at least 26 others were also wounded.
Democratic presidential candidates have criticised the US leader after the mass shootings, saying his language against minorities promotes racial division and violence.
Beto O’Rourke, who was born in El Paso, told CNN: “Let’s be very clear about what is causing this and who the president is.
“He is an open avowed racist and is encouraging more racism in this country.”
Another Democratic candidate, Pete Buttigieg, said Republican Mr Trump was “condoning and encouraging white nationalism”.
New Jersey Senator Cory Booker said: “There is complicity in the president’s hatred that undermines the goodness and the decency of Americans regardless of what party.”
Mexico President Andres Manuel Lopez Obrador said six Mexicans were killed in the El Paso shooting.
He added that the events in Texas reaffirmed his conviction that “social problems shouldn’t be confronted with the use of force and by inciting hate”.
In the past, Mr Trump has called some Mexican immigrants “rapists” and “criminals”.
Amid calls from anti-gun campaigners for tighten controls, America’s National Rifle Association (NRA) said it was “committed to the safe and lawful use of firearms by those exercising their Second Amendment freedoms”.
“We will not participate in the politicising of these tragedies but, as always, we will work in good faith to pursue real solutions that protect us all from people who commit these horrific acts”.
A local prosecutor has announced he will bring capital murder charges against Crusius and said he had “lost the right to be among us” after the Texas shooting.
In the Dayton shooting, Betts was armed with a .223-caliber rifle with magazines capable of holding at least 100 rounds of ammunition.
He was killed at an entrance to a bar where people were taking cover, police chief Richard Biehl said.
Mr Biehl added that if Betts had managed to get inside, the result would have been “catastrophic”. Police have not yet identified a motive.
If Sandy Hook wasn’t enough to inspire change, whatever will be? – Analysis by Cordelia Lynch, US correspondent
Twin tragedies in 24 hours and America’s haunting relationship with guns plays out in the grimly familiar fashion I have sadly come to expect covering the United States.
I was in Orlando, Florida, when 49 people were killed in a gay nightclub. I interviewed the gunman’s father.
In Parkland, I spoke with terrified friends of the 17 students and staff members who died after a young man opened fire at Marjory Stoneman Douglas High School who died.
At least nine people have been shot dead outside a bar in Ohio, just hours after 20 people were killed in a shooting at a Walmart in Texas
In Las Vegas, I sat down with family members of some of the 58 people who were killed. And in Dallas, I met those taking up arms in response to five police officers who were fatally shot in the line of duty. The list goes on.
Mass shootings are now so commonplace in news coverage that we have to decide which ones we travel to report on.
As a team you find yourself having to decide on a bar. Are there more than 10 dead? Is there a motivation emerging? Are there broader issues at play that it speaks to?
The last time I was in El Paso, I interviewed the mayor, Dee Margo, for a film about Donald Trump’s border wall.
I witnessed the high number of immigrants going through the courts in the border city. It is a place full of hope and despair.
Mr Margo was articulate and proud of the diversity of his city, despite the challenges. On Saturday afternoon, I’m listening to his voice breaking as he discusses the shock of what’s unfolded. I instantly wonder if immigration has a part to play in the story. It now appears it did.
Walmart has its own curious part to play in this dark tale – one that illustrates just how mainstream and monetised America’s gun culture is. The outlet is often referred to as the world’s largest gun retailer.
Sam Walton, the founder of Walmart, opened his flagship shop in Bentonville, Arkansas, specifically so he could be close to his in-laws’ quail hunting ranch.
The shooting in El Paso is the second to take place in one of its shops in just a week.
With the country still grieving, Dayton’s mayor Nan Whaley made a point of noting that their’s was just the latest. She said her city was the 250th to experience a mass shooting this year.
The places change and so do the numbers, but for those who want to kill a lot of people, guns are often the weapon of choice.
After the Las Vegas shooting in 2017, the worst in this country’s history, there was bi-partisan support for background checks. That bill would prevent people who have been convicted of abusive behaviour from buying or owning firearms.
But as presidential candidate Amy Klobochaur pointed out, “that bill is sitting on Mitch McConnell’s doorstep because of the money and the power of the NRA [National Rifle Association]”.
The Democratic contenders for president are largely in agreement on the need for greater gun restrictions. Almost every candidate in the field supports universal background checks and bringing back a ban on the sale of “assault” weapons like the one that expired in 2004.
But President Trump and Mike Pence stopped short of calling for action on gun violence and many of their supporters will be relieved.
If Sandy Hook wasn’t enough to inspire change, whatever will be? I dearly hope I’m wrong.