State Rep. Chris Sgro, D-Guilford, who is also executive director of Equality NC, leads a group carrying petitions calling for the repeal of House Bill 2 to Gov. Pat McCrory's office at the state Capitol building Monday, April 25, 2016, in Raleigh, N.C. Tempers are flaring as supporters and opponents of the new North Carolina transgender law hold competing rallies to sway legislators starting their annual session.

RALEIGH, N.C. — Demonstrations encircled North Carolina's statehouse Monday, for and against a Republican-backed law curtailing protections for LGBT people and limiting public bathroom access for transgender people.

At least 18 protesters opposing the law were arrested when they entered the office of a top legislative leader.

Thousands of Christian conservatives and other supporters of the law known as House Bill 2 gathered on a grassy mall behind the Legislative Building on the legislature's opening day to praise the mostly Republican legislators and GOP Gov. Pat McCrory for passing the restrictions last month in a special session.

"It took great courage for them to establish this bill," said Doug Woods, 82, of Raleigh, a rally participant. "They need to stand firm."

The law blocks local and state protections for lesbian, gay, bisexual and transgender people and directs which restrooms transgender people can use in public buildings. Key lawmakers who pushed through the legislation also urged the rally attendees to contact colleagues and fight off efforts to overturn the law.

"The battle is about to be engaged," said Rep. Paul Stam, R-Wake, a veteran of North Carolina's cultural wars, addressing the crowd.

Later Monday afternoon and evening, hundreds of protesters took turns sitting outside the offices of House Speaker Tim Moore and Senate leader Phil Berger to demand repeal of the law

Police led away 18 people Monday evening from Moore's office in plastic handcuffs. They were going to be charged with second-degree trespassing, acting General Assembly Police Chief Martin Brock said. One man who had to be carried out by officers also was facing a charge of resisting arrest, according to Brock.

Most were led off quietly, but one woman chanted: "Forward together, not one step back!"

Among those led out in handcuffs was Mara Keisling, executive director of the National Center for Transgender Equality in Washington.

North Carolina legislators returned Monday night for their annual work session. As the short House meeting ended, demonstrators in the gallery yelled their displeasure. Several dozen protesters continued a vocal protest inside the front doors of the Legislative Building for at least a half hour before leaving. About two dozen others remained

"We won't do HB 2," the protesters chanted, referring to the law by its initials. "North Carolina sticks together."

Earlier Monday, about 200 people gathered on the grounds of the old Capitol building to hear speakers denounce the law. They carried cardboard boxes holding what they said were 180,000 pro-repeal signatures on a petition for delivery to McCrory, whose office sits within the 1840 Capitol building. By mid-afternoon their numbers reached between 600 and 800.

"HB2 compounds the discrimination and marginalization of the transgender community, who already have to fight every day for their survival," said Joaquin Carcano, a transgender man who's suing over the law. "Our privacy and safety matter too. Our right to feel safe and protected in this world does not infringe on anyone else's right to the same."

The head of the state NAACP, the Rev. William Barber, called the law "Hate Bill 2." He said it affects the poor and minorities as well as the LGBT community, despite conservative efforts to depict it as a law focused on bathroom safety.

"We make a mistake when we call it the 'bathroom bill,'" he said.

Republican legislative leaders have expressed no interest in overturning the new law. GOP lawmakers have focused their discussion of the law on provisions requiring transgender people to use multi-stall restrooms that align with their gender at birth.

North Carolina House Democrats filed legislation Monday to repeal the law, though a lack of Republican sponsors made its chances appear slim.

Democratic Rep. Grier Martin of Raleigh, a sponsor of the repeal bill, said the new law has stained North Carolina's reputation and harmed it economically. Some companies have halted planned expansions because of the law. Many groups have canceled scheduled conventions in the state.

If the repeal were approved immediately, Martin told reporters, "it would not undo with the swipe of a pen the incredible damage that House Bill 2 has done to our economy. But it would stop the bleeding and put North Carolina back on the path of progress."

Moore and McCrory said separately Monday that the law won't be repealed this session. A repeal is "not going to happen," McCrory told reporters in Wilmington, although he wants a portion removed that appears to prevent workers from suing in state court under an employment non-discrimination law.

Berger has said he sees no need for a repeal. He said Monday night he hadn't heard from any colleagues whose support for the law had been swayed based on the protests and economic fallout.