US President Donald Trump has been criticised on social media over his reaction to the deadliest mass shooting in the country's modern history.

At least 58 people were killed and more than 500 others injured on Sunday when a gunman opened fire on a crowd of concert-goers in Las Vegas, Nevada.

The attacker, named by police as Stephen Paddock, was found dead in a room on the 32nd floor of the Mandalay Bay hotel, from where he is believed to have carried out the attack.

In a televised speech on Monday, Trump expressed his "warmest condolences", calling the attack "an act of pure evil".

READ MORE: Las Vegas Mandala Bay shooting: What, where and who?

He also praised local law enforcement for their rapid response to the shooting.

Trump's first reaction came hours after the mass shooting took place, when he tweeted that the attack was a "terrible" tragedy.

Many on social media felt Trump's reaction on Twitter, and later during his speech was too little, too late.

Donald Trump responded to the London Bridge attack in 2 hours, Parsons Green explosion in 3. Now 5+ hours since Las Vegas and still silent. — Lizzie Dearden (@lizziedearden) October 2, 2017

No Trump tweets yet abt the #LasVegas shooting. What is he waiting 4? 2 find out the shooter is/isn't white? Now is a good time 2 b a leader — Sherri ☠️TWDFan4Ever (@Specneedsmom4) October 2, 2017

Trump who is all the time active on Twitter hasnt tweeted yet on #LasVegas. Sleeping ? No tweets from @DHSgov or @WhiteHouse either. — hachiko (@hachik012) October 2, 2017

US police revealed on Monday that Paddock had in excess of 10 guns in his hotel room, renewing the debate over gun control in the US.

Since taking office, Trump has raised the issue of gun ownership rights only obliquely at a few of the campaign-style rallies he has held.

But he has taken steps to roll back some restrictions on gun use and sales put into effect while his predecessor, Barack Obama, was in office.

My heart goes out to the people of Las Vegas. This is a senseless tragedy. Please Mr Trump, gun reform must happen now. #LasVegas — Joel Ainsworth (@Joel_Ainsworth) October 2, 2017

"Las Vegas" Presumaby #Trump will now issue a complete and total ban on Americans entering the United States of America. Or ban guns maybe — Scott Tracey (@Hammersfanno) October 2, 2017

#LasVegas Is it normal in the States to carry machine guns around? Uuups, Trump is President and yes it is normal. Sad, very sad!!! — Manukay (@Manukay1) October 2, 2017

Replying to reporters' questions on gun control on Monday, Sarah Huckabee Sanders, the White House press secretary, said there is a "time and place" for a debate but that is "not the place we're in at this moment".

She said Trump was focused on the victims and stressed that it was a "time to unite the country".

Obama frequently used mass shootings to call for stricter gun control laws.

Some social media users also condemned Trump for not calling the Las Vegas shooter a "terrorist", with many pointing to what they say is a double standard in the way white attackers and non-white attackers are labelled and treated in the US.

A non-exhaustive comparison of the response by President Trump to terror attacks depending on whether the perpetrator(s) or victims are Muslim #disappointing pic.twitter.com/qPbsAtULus — Miqdaad Versi (@miqdaad) October 2, 2017

Hard to listen to this Trump statement and not wonder how different it would be if the shooter were known to be Muslim — Zack Beauchamp (@zackbeauchamp) October 2, 2017

"I can't get into the mind of a psychopath" Vegas Police Chief. Yet if perpetrator had been Muslim, Trump would immediately blame religion. — Guthrie 🙏✌️ (@GuthrieGF) October 2, 2017

Las Vegas shooter identified as Stephen Paddock, 64, a Las Vegas local…Why won't Trump call out this violent DOMESTIC terrorism? — Cyrus Sanati (@BeyondBlunt) October 2, 2017

#domesticterrorism hits Las Vegas. Death toll up to 50. This, Mr #Trump , is the real terror threat to Americans!https://t.co/vPRZxj3e9U — Cheetahkit Dolcini (@CheetahkitD1) October 2, 2017

Sunday's attack is the deadliest mass shooting in modern US history.

So far in 2017, the watchdog group Gun Violence Archive has documented 273 mass shootings in the country.