Police in the US state of Florida has charged a 19-year-old suspected of shooting students and adults at his former school with 17 counts of premeditated murder.

The man, identified as Nikolas Cruz, was accused on Thursday of opening fire the previous day at a high school in the town of Parkland, in one of the deadliest mass shootings in modern US history.

Authorities warned late on Wednesday that the death toll could rise, as some of the 15 wounded people were in critical condition and undergoing surgery.

Police said Cruz had been expelled from Marjory Stoneman Douglas High School for disciplinary problems. On Thursday, the leader of white supremacist group in Florida confirmed that Cruz had been a member.

The 19-year-old was taken into custody shortly after the shooting.

Officials said the gunman began shooting outside the school at about 2:40pm local time (19:40 GMT) on Wednesday. Some students believed a fire drill was taking place.

The attacker, armed with a semiautomatic AR-15 rifle, a gas mask, smoke grenades and "multiple magazines" of ammunition, entered the school and continued his rampage.

Those inside the school can be heard yelling "Oh my God!" as shots rang out in videos circulating on social media.

A student told local media he had to wait in a closet while the school was under a "code red" lockdown.

"I was just in disbelief. I was texting my friends and my family," the student told WPTV-TV, an NBC affiliate in West Palm Beach, Florida, after being evacuated from the school.

"I didn't believe it was actually happening," he said.

The gunman then fled the scene and was taken into custody about an hour later in a neighbouring city, officials said.

"It is a horrific situation," Broward County public school Superintendent Robert Runcie told The Associated Press. "It is a horrible day for us," he added.

17 people were killed in the deadliest high school shooting in U.S. history. pic.twitter.com/FXYB2hyKSR — AJ (@ajplus) February 15, 2018

Sheriff Scott Israel called the shooting "catastrophic", saying that "there really are no words".

"My prayers and condolences to the families of the victims of the terrible Florida shooting," US President Donald Trump said. "No child, teacher or anyone else should ever feel unsafe in an American school," he added.

More than a dozen school shootings in 2018

Everytown for Gun Safety Support Fund, an organisation advocating for gun control, had recorded 17 shootings at schools this year alone prior to Wednesday's incident in Florida.

Everytown defines a school shooting as "any time a firearm discharges a live round inside a school building or on a school campus or grounds".

At least two of the shootings were classified as attempted or completed suicides with no intent to harm others. At least one occurred when a gun unintentionally discharged.





In January, a 15-year-old male student allegedly opened fire at a high school in Benton, Kentucky, killing one person and injuring more than a dozen others.

Nearly 300 school shootings have been reported since 2013 across the US, Everytown said.

Wednesday's shooting is among the 10 deadliest mass shootings in modern US history.

It has again renewed the debate surrounding gun control in the US.

Last year, a gunman opened fire on a church in Texas, killing 26 people. About a month earlier, another attacker killed at least 58 people at a concert in Las Vegas, Nevada.