NEW YORK - New York Governor Andrew Cuomo on Tuesday signed into law one of the nation's toughest gun-control measures and the first to be enacted since the mass shooting last month at an elementary school in neighboring Connecticut.

The bill passed the Democratic-led Assembly on Tuesday afternoon, a day after sprinting through the Republican-majority Senate. State lawmakers have been in session for just a matter of days.

New York's legislation comes just a day before President Barack Obama is expected to propose a national assault weapons ban and improved background checks as part of a sweeping package of initiatives to curb gun violence in the wake of the Sandy Hook Elementary School massacre.

Twenty 6- and 7-year-old schoolchildren and six educators were killed in the Dec. 14 attack, when a man burst into their school in Newtown, about 70 miles (112 km) northeast of New York City, and opened fire with a semi-automatic weapon.

The Sandy Hook shooting plunged the nation into grief and reignited the gun-control debate.

Cuomo acted swiftly following that attack and another 10 days later in Webster, New York, a suburb of Rochester, that claimed the lives of two volunteer firefighters. The new law mandates a life sentence without parole for anyone who murders a first responder, the so-called "Webster Provision."

With some provisions due to take effect immediately, the legislation expands the state's ban on assault weapons, puts limits on ammunition capacity and has new measures to keep guns out of the hands of the mentally ill.

"People who are mentally ill should not have access to guns, that's common sense," Cuomo said at a signing ceremony in Albany. "That's probably the hallmark of this bill, coming up with a system that allows for mental-health screens."

The measure limits magazine capacity to no more than seven cartridges - the current limit is 10 cartridges - and requires a statewide re-registration of all handguns and grandfathered assault weapons.

"Seven bullets in a gun, why? Because the high-capacity magazines that give you the capacity to kill a large number of human beings in a very short period of time is nonsensical to a civil society," Cuomo said.

Police have said the gunman in Newtown, 20-year-old Adam Lanza, carried numerous high-capacity magazines and that he changed gun clips several times, allowing him to unleash at least 150 rounds in his 10-minute assault.

Gun rights advocates lashed out at Cuomo and New York's law, decrying the speed at which the legislation moved through the statehouse.