In the US state of Ohio, voters have rejected proposals to make marijuana legal, according to local media projections.

The measure, known as Issue 3, would have amended the state constitution to legalise the personal and medical use of marijuana for anyone over 21.

But it was defeated by nearly a two-to-one margin, the projections said.

Pro-legalisation campaigners spent about $12m in advertising in the run-up to Tuesday's vote.

Issue 3 would have granted rights for marijuana to be grown commercially at 10 sites across Ohio, which critics said could have created a monopoly.

The legalisation measure would have allowed marijuana, pot-infused sweets and other related products to be purchased in stores. Home-growers could keep up to four flowering marijuana plants.