WASHINGTON - Lawmakers in the southeastern US state of Florida have passed a gun-control legislation in a bid to boost school safety, three weeks after 17 people were shot dead on a high school campus in Parkland, Florida.

The bill, the first major gun-control state law in Florida in decades, now goes to Republican Governor Rick Scott for his signature.

The measure narrowly passed the state Senate in a 20-to-18 vote on Monday before sailing through the House of Representatives on Wednesday in a 67-50 vote. Both the state House and Senate are controlled by Republicans.

Under the bill, the minimum age to buy any type of gun is raised to 21 years old from 18, though with some exceptions. The buyers also need to wait for three days before receiving a firearm in most cases.

The measures also include banning the sale of bump stocks that can make semiautomatic rifles perform like fully automatic ones, investing $400 million in improving mental-health services and boosting physical security of school buildings, as well as a controversial "guardian" program to train and arm some voluntary school personnel.

However, facing opposition from Governor Scott and many residents in Parkland, the "guardian" program will exclude people who exclusively perform classroom duties, said local media reports.

The legislation also excludes proposals to ban assault weapons like AR15 and other semiautomatic rifles.

Also on Wednesday, Nikolas Cruz, the 19-year-old suspected shooter, was formally indicted on murder charges over the shooting at Marjory Stoneman Douglas High School in Parkland on Feb 14, leaving 17 killed and 14 others injured.