Gun auction platforms are reporting a significant price increase for bump stocks just hours after President Donald Trump directed the Justice Department to move to ban similar devices, Bloomberg reported.

A bump stock is an attachment that allows a semi-automatic rifle to mimic a fully automatic weapon's "cyclic firing rate to mimic nearly continuous automatic fire," according to the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).

"We must do more to protect our children," Trump said, adding that his administration was working hard to respond to the shooting in Parkland, Fla., that left 17 dead.

Bloomberg reported that some firearms auction platforms are listing the bump stocks and adding “get them while you can, guys.” Bump stocks can often sell for less than $200, but the report said some auction prices hit $1,000.

After past mass killings yielded little action on tighter gun controls, the White House is trying to demonstrate that it is taking the issue seriously.

The president, a strong and vocal supporter of gun rights, has not endorsed more robust changes sought by gun control activists. But the White House cast the president in recent days as having been swayed by the school shooting in Florida and willing to listen to proposals.

In a tweet Tuesday night, Trump indicated he wants to strengthen the background check system, but offered no specifics. Trump said: "Whether we are Republican or Democrat, we must now focus on strengthening Background Checks!"

Asked at a press briefing Tuesday if Trump was open to reinstating a ban on assault-type weapons, spokeswoman Sarah Huckabee Sanders said White House officials "haven't closed the door on any front." She also said that the idea of raising the age limit to buy an AR-15 was "on the table for us to discuss."

Sen. Chris Murphy, a Connecticut Democrat and leading advocate for tighter gun controls, said Trump's directive suggested the president was aware of fresh energy on the issue and called it a sign that "for the first time" politicians are "scared of the political consequences of inaction on guns."

A bipartisan legislative effort to ban bump stocks last year fizzled out. The ATF announced in December that it was reviewing whether weapons using bump stocks should be considered illegal machine guns under federal law.

Under the Obama administration, the ATF had concluded that bump stocks did not violate federal law. But the acting director of the ATF told lawmakers in December that the ATF and Justice Department would not have initiated the review if a ban "wasn't a possibility at the end."

The Justice Department had not made any announcement regarding its review when Trump on Tuesday signed a memorandum directing the agency to complete the review as soon as possible and propose a rule "banning all devices that turn legal weapons into machine guns."

Reacting to Trump's memo, the department said in a statement that it "understands this is a priority for the president and has acted quickly to move through the rulemaking process. We look forward to the results of that process as soon as it is duly completed."

A day earlier, Trump sent another signal he had been swayed by the Parkland shooting and the dramatic calls for action in its aftermath.

A White House statement said Trump was looking at a bill that would strengthen federal gun background checks. On Wednesday, he will host parents, teachers and students at the White House for a "listening session" that will include people impacted by mass shootings in Parkland; Littleton, Colo.; and Newtown, Conn].

The president was moved by a visit Friday with Florida victims in the hospital and is trying to work on solutions, said a person familiar with his thinking who sought anonymity to discuss internal conversations.

Among the steps sought by gun control advocates: closing loopholes that permit loose private sales on the internet and at gun shows, banning assault-type weapons and to passing laws to enable family members, guardians or police to ask judges to strip gun rights temporarily from people who show warning signs of violence.

The Parkland shooting also has prompted the Republican-controlled Florida Legislature to take a fresh look at gun control legislation, although so far GOP leaders are refusing to endorse calls to ban assault rifles. Still, the discussion of some types of gun control legislation is a dramatic turnaround for Florida, which has earned the nickname the "Gunshine State" for its gun policies.

The Associated Press contributed to this report