Young survivors of last Wednesday's school shooting in Florida have announced that they are planning a national march on Washington to demand political action on gun control, while Donald Trump was attacked for playing politics over the tragedy.

Student organisers told US media outlets that they were determined to make the shooting, which left 17 students and staff members dead, a turning point in the national gun debate. The attack was the deadliest US school shooting since 2012.

Yesterday, student survivors from Marjory Stoneman Douglas announced their March for Our Lives campaign. They are planning to march on Washington on March 24 to demand that children and their families 'become a priority' for US lawmakers, and hope that other protests will take place simultaneously in other cities on the same day.

'We are losing our lives while the adults are playing around,' said Cameron Kasky, a survivor from the school.

Meanwhile, Trump attacked the FBI and lawmakers probing suspected Russian meddling in the 2016 US presidential election, drawing sharp criticism for saying an excessive focus on Russia led investigators to miss signs that could have prevented the deadly school shooting in Florida.

In a series of tweets over the weekend from his Mar-a-Lago estate in Florida, Trump said congressional investigations and political 'hatred' showed Russia had succeeded in sowing 'discord, disruption and chaos' in the United States.

He accused his Democratic predecessor as president, Barack Obama, of failing to do enough to stop Russian election interference.

'They are laughing their asses off in Moscow,' Trump tweeted on Sunday morning.

In a tweet on Saturday night, Trump criticised the FBI for missing warning signs in the case of Nikolas Cruz, 19, who is charged with killing 17 people on Wednesday at the school.

The FBI acknowledged on Friday that it failed to investigate a warning that Cruz possessed a gun and the desire to kill.

'Very sad that the FBI missed all of the many signals sent out by the Florida school shooter. This is not acceptable,' Trump wrote. 'They are spending too much time trying to prove Russian collusion with the Trump campaign – there is no collusion,' he added.

The Republican president offered no evidence of any link between the investigation of Russian meddling and the FBI's failure to prevent the Florida shooting.

Student survivors of the massacre slammed Trump for connecting it to the Russia probe, which has shadowed his year-old presidency.

'Oh my god. 17 OF MY CLASSMATES AND FRIENDS ARE GONE AND YOU HAVE THE AUDACITY TO MAKE THIS ABOUT RUSSIA???!!' Morgan Williams, 16, tweeted. 'HAVE A DAMN HEART.'

Several lawmakers, including a fellow Republican, also rejected Trump's linking of the FBI's missteps in preventing the shooting to the Russia probe.

'So many folks in the FBI are doing all that they can to keep us safe. The reality of it is, is that they are two separate issues,' Republican Senator Tim Scott said on CBS' 'Face the Nation' programme.

Former Deputy Attorney General Sally Yates tweeted: 'Our president uses the tragedy to attack the investigation of a foreign adversary's interference in our democracy. Shameful.'

Yates, who had been a holdover from the Obama administration, was fired early in the Trump presidency for refusing to defend travel restrictions on several Muslim-majority countries.

Additional reporting by Reuters.