Patrick Crusius posted a four-page white supremacist "manifesto" that railed against Hispanics

The mother of a young man suspected of gunning down 22 people at a Walmart in the US state of Texas called police weeks before, concerned about a military-style weapon he owned, the family's lawyers told CNN.

The report comes with bipartisan sentiment for action on gun safety appearing to grow after the killings in El Paso and another mass shooting hours later in Dayton, Ohio that left nine people dead.

CNN reported that the mother of the El Paso suspect, Patrick Crusius, had called police in the Dallas suburb of Allen weeks before the attack because she was concerned about his owning an "AK"-type firearm, the network quoted family lawyers as saying.

AK usually refers to a Kalashnikov, a type of semi-automatic rifle.

The lawyers, Chris Ayres and R. Jack Ayres, of Dallas, told CNN that Crusius's mother was worried given her son's age, maturity level and lack of experience with such a weapon.

They added that, during the call, a police officer told her that -- based on what she described -- her 21-year-old son was legally able to purchase the weapon.

But the mother's call was "informational" and not motivated out of a concern that her son posed a threat, the lawyers said, adding the mother did not give police her name or her son's name.

"This was not a volatile, explosive, erratic behaving kid," CNN quoted Chris Ayres as saying. "It's not like alarm bells were going off."

Chris Ayres could not immediately be reached when AFP contacted his law office.

Asked about the CNN report, Sergeant Jon Felty, of the Allen Police Department, told AFP: "I have nothing in our database to support this claim."

About 20 minutes before the rampage with a semi-automatic weapon, Crusius, who is white, posted a four-page white supremacist "manifesto" on the online forum 8chan that railed against Hispanics.

Several of those killed were Mexicans.

After the shootings, US President Donald Trump faced protests that his rhetoric on race has fuelled extremism.

In an address to the nation on Monday, Trump rejected racism and white supremacist ideology, and said he supported "red flag" laws allowing authorities to confiscate weapons from people believed to present grave risks.