Students who organised massive demonstrations for stricter gun laws in Washington and across the United States say the turnout exceeded their expectations.
March For Our Live organisers say more than 850,000 people marched in Washington on Sunday, though no official estimate of the crowd size has been released.
"You showed up! More than 850,000 marched with us in DC yesterday. Together, we are so powerful," organisers tweeted.
The march, along with more than 800 sister marches in cities and towns around the world, is being compared with student-led marches against the Vietnam war in the '60s and '70s.
Marchers are demanding a ban on the sale of assault weapons like the AR-15 used by the shooter in last month's shooting at a school in Parkland, Florida, a ban on the sale of high-capacity magazines and stricter background checks for gun purchasers.
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Several teenagers who experienced gun violence delivered emotional speeches at the march in Washington. Among them were survivors of the shooting at Marjory Stoneman Douglas High School in Parkland, Florida, where a gunman killed 17 people on February 14.
Some of the speakers took aim at the National Rifle Association, a politically active lobbying group that donates large amounts of money to politicians.
The NRA's response was an advertisement on Facebook urging people to "stand and fight for our kids' safety by joining NRA."
It said the marches were supported by "gun-hating billionaires and Hollywood elites" who are exploiting children as part of a plan to destroy US citizens' rights to own guns.
