DENVER (AP) - Colorado's governor will sign legislation on Wednesday that sets limits on ammunition magazines and expands background checks for firearms, marking a Democratic victory in a state where a debate over gun rights has played out in the wake of two mass shootings.

The measures proposed are some of the strictest gun laws in the United States, and their passage comes after weeks of tense legislative battles.

Republicans and gun rights supporters put up a major fight against the measures in this politically moderate state, while Democrats made them the centerpieces of a package of legislative proposals drafted in reaction to shooting rampages at a suburban Denver movie theatre and a Connecticut elementary school last year.

"I think it will make it more difficult for people to get guns who shouldn't have them, and that's really the goal," said Democratic Representative Beth McCann on the expanded background checks.

Magazine limits would reduce gun violence and have an impact during mass shootings, because they would force gunmen to reload more times, she said. "It's an interruption in the spraying of bullets."

Colorado Governor John Hickenlooper's spokesman Eric Brown confirmed on Monday that the governor would sign the measures.

Colorado's gun controls, which become effective on July 1, are the first beyond East Coast states approved this year.

They also are getting approval as Congress embarks on its own gun debate in Washington, where Colorado Democrats' proposals were closely watched because the state is seen as a bellwether.

Gun control has become a major national issue in the wake of the mass shootings last December at Sandy Hook Elementary School in Newtown, Connecticut that left 20 children and six staff members dead. Last July, a gunman opened fire in a crowded movie theater in Aurora, Colorado, killing 12 people and wounding about 70.

The Colorado laws include a ban on ammunition magazines that can carry more than 15 rounds, and eight shotgun shells. The bill on background checks expands the requirement to sales and transfers between private parties and online purchases.

Republicans reviled both bills and argued the proposals would not prevent more shootings, but only deprive law-abiding citizens of exercising their constitutional right to bear arms guaranteed by the Second Amendment.

"We're obviously very disappointed. I think we demonstrated time and time again all of the issues associated with" the magazine limits, said Mr Mark Waller, the Republican leader in the state House.

"They're doing this without any proof that banning this is going to have any impact on public safety," he said.

Republicans seemed resigned from the start that the bills would become law, though. Mr Hickenlooper said previously he would sign the magazine limit, and he specifically asked the Legislature to expand background checks in his annual address.

The governor also was planning to sign a bill reviving user fees for gun purchasers needing background checks.

Colorado charged US$10 (S$12.50) background-check fees more than a decade ago, but the fees were dropped. The Colorado Bureau of Investigation currently picks up the tab checking prospective gun owners.

A Colorado-based magazine manufacturer said it would leave the state if the new restrictions were passed, taking hundreds of jobs with it. Democrats tried to ease the concerns from Magpul Industries, saying the company can still manufacture higher-capacity magazines if they were sold out of state.

Other Democratic gun control proposals still pending in the state Legislature include a ban on gun ownership by people accused of domestic-violence crimes and a bill to eliminate online-only safety training for people seeking concealed-weapons permits.

Two more Democratic gun control bills were withdrawn when they appeared to lack support for passage. Those included a new liability standard for gun owners and sellers, and a ban on concealed weapons on public college campuses.

Republican gun ideas were hastily rejected earlier this year. Those ideas included expanding gun laws to allow teachers to carry concealed weapons, and a failed attempt to require armed security guards at businesses that ban concealed weapons.