Hundreds of thousands of Americans galvanised by last month’s Florida school massacre rallied in cities across the country on Saturday to demand tighter gun laws.

The massive March For Our Lives rallies, some led by student survivors from Parkland, aim to break legislative gridlock that has long stymied efforts to increase restrictions on firearms sales in a nation where mass shootings like the one on Feb. 14 at Marjory Stoneman Douglas High School have become frighteningly common.