WASHINGTON - US?President Donald Trump suggested on Thursday that he supports raising the minimum age to buy assault-style weapons, while vowing to push for background checks.

"I will be strongly pushing Comprehensive Background Checks with an emphasis on Mental Health," Trump said in a series of tweets Thursday morning.

Trump's remarks came amid renewed calls and protests for gun restrictions after a 19-year-old gunman, described as mentally troubled, killed 17 people with an AR-15 style assault rifle at a high school in the state of Florida last week.

"Raise age to 21 and end sale of Bump Stocks," Trump said. "Congress is in a mood to finally do something on this issue - I hope!"

Per US federal laws, people must be at least 21 years old to buy a handgun from a licensed dealer, but they have to be only 18 to purchase a rifle or shotgun.

Trump said earlier this week that he has recommended that "bump stocks," devices that enable semi-automatic weapons to fire hundreds of rounds per minute, be banned.

A professional gambler killed 58 people with rifles fitted with bump stocks in Las Vegas, the US state of Nevada, last October.

Trump also suggested the possibility of arming teachers as he vowed strong background checks and mental health screenings for gun buyers during a televised White House meeting with those affected by school shootings on Wednesday.

In one of the tweets Thursday, Trump clarified that what he said was to look at the possibility of giving "concealed guns to gun adept teachers with military or special training experience."

He said that highly-trained, gun-adept educators, if armed, would act before police and first responders get to the shooting site, and they would also serve as a deterrent to would-be gunmen.

"Must be offensive, defense alone won't work," Trump added.