Nikolas Cruz, the former student accused of a 2018 shooting rampage at a high school in Parkland, Florida, will plead guilty to murdering 17 people, his lawyer has told a US court.

"It is our intent to enter a change of plea as to both cases, to all charges," attorney David Wheeler confirmed in the Broward County courtroom.

He indicated that Cruz, now aged 23, would drop his initial innocent plea both for the murders and for physically attacking a jail officer after his arrest.

A former student at Marjory Stoneman Douglas High School, Cruz was expelled for "disciplinary reasons".

He was 19 when he took a legally purchased AR-15 assault rifle into his former school, killing 17 students and staff members.

The St Valentine's Day attack was the country's worst US school massacre since the horror at Sandy Hook Elementary School in Newtown, Connecticut in 2012, which left 26 dead.

Cruz was charged with 17 counts of premeditated murder and 17 counts of attempted murder for those he wounded in the attack.

The shooting sparked new efforts, led by students from the school itself, for tougher gun controls - although the polarised US Congress has yet to enact meaningful gun reform.

Cruz bought the weapon legally, despite having been in local records as having a history of mental health problems.

When he was arraigned on 13 March 2018, a "not guilty" plea was entered as prosecutors said they would seek the death penalty in the case.

At the time, his lawyers let it be known that he would offer a guilty plea if the death penalty was taken off the table. It is not clear if any such deal had been reached.

In reaction to the news, Fred Guttenberg, whose 14-year-old daughter Jaime was killed in the attack, called on people to "remember the victims."

"Remember Jaime," he wrote on Twitter.

Police at Marjory Stoneman Douglas High School the day after the shootings

Twelve of the victims were killed inside the school building, two others just outside, one more on the street and two other victims died as a result of their injuries at a hospital.

Irish teenager Adelina Hurley, a student at the school, recounted how she had to run for her life as the attacker fired his gun.

She said a teacher guided pupils out of the school and took a secret route to a local shopping centre.

"It was really scary because everyone was running, screaming and some people were crying. People were like climbing the fence just to get out as fast as they could."