A group of undocumented immigrants has occupied President Barack Obama's campaign office in downtown Oakland, refusing to leave until his administration stops deporting students.

"We're going to stay here as long as we can," said Luis Serrano, 24, speaking by cell phone Thursday evening from inside the Telegraph Avenue storefront where he and other students were staging a sit-in.

Serrano, three other illegal immigrant students and a supporter walked into the Obama for America office on Thursday afternoon pretending to be campaign volunteers.

"They said they were going to do some phone banking and donations," said activist Krsna Avila of the National Immigrant Youth Alliance, which organized the protest.

Soon after arriving, however, the students plopped down, put graduation caps on their heads and informed local campaign workers they would not leave until Obama changed his deportation policy.

"We're asking him not to deport these students," Avila said.

The Obama campaign has not yet sought to kick them out, and instead hired a local security firm to keep watch over the students and the office overnight. Security guards could be seen in a heated discussion with the protesters inside the building on Thursday evening.

On the front door of the office the protesters put up a sign: "Closed due to deportations."

The sit-in is part of a national campaign to disrupt Democratic campaign offices. Protesters want an executive order from Obama halting deportations of young people brought to the country illegally when they were minors.

Students took over Obama's Denver campaign headquarters in a similar protest last week, sparking a round of sit-ins now erupting in Los Angeles, Michigan and Ohio.

"Our communities are being empowered by what we're doing," said Blanca Vazquez, 22, also speaking by phone from inside the building.

The San Francisco State student from Oakland said she has been living in the United States since she was 6 months old but has been unable to get legal residency.

"We have to stand up. We can't be afraid anymore. We've gone through generations of people being afraid, staying quiet," Vazquez said. That, she said, "is not working anymore."