SAN FRANCISCO -- San Francisco police arrested 18 people Monday evening during a demonstration in which unionized employees blocked part of Market Street in protest of layoffs and wage reductions.

Some of them sat in the street at the corner of Market and Ninth Streets, protesting what they said is Mayor Gavin Newsom's plan to eliminate city jobs.

Protesters marched from City Hall to Market Street and, at about 6 p.m., a circle of demonstrators blocked the intersection of Market and Ninth. Police Lt. Lyn Tomioka said 18 protesters were arrested at the intersection for obstructing traffic.

The protest shut down street traffic including Muni lines, which had to detour around the busy intersection.

The workers said they're the lowest paid employees in city government and they'll be suffering the most from the cuts. They said their street protest was a way to draw attention to their plight.

Carlos Rivera of SEIU Local 1021 put the protest in an historical context.

"Mayor Newsom has decided to do 500 layoffs and wage cuts to women and people of color," he said. "So when that happens you have to stand up and fight back, that's what Martin Luther King did, that's what Rosa Parks did."

Karen Bishop was one of those arrested. She said she's standing up for school district employees who may lose their jobs just before the holidays.

"We have about 60 secretaries that are going out the door that are being laid off right before these holidays and you know secretaries are an important part of the school community," the SEIU executive board member said.

City health care workers said they are being hit even harder. Certified nurses complained their jobs are being reclassified to lower paying positions and even those who keep their jobs will likely take pay cuts.

"The jobs cut first and then they are offered another position with another name but it's the exact same position with just another name on it and less pay," said certified nursing assistant Debbie Dobson.

Teresa Rutherford, a nurse at Laguna Honda Hospital, said it would affect her entire income. "I have kids in college," said Rutherford. "I have a mortgage to pay."

The demonstrators were cited and released, Tomioka said.

The city workers said federal stimulus funds expected in April would cover the budget gap for health care workers. They added they don't understand why the mayor won't promise to save their jobs with federal funds.

KTVU tried to contact Mayor Newsom, but he was unavailable for comment Monday night.

Service Employee International Union Local 1021 officials said that the layoffs could be prevented by a budget appropriation to be considered by the Board of Supervisors on Tuesday.