Hundreds of churches in the United States are offering to open their doors to undocumented migrants, a few weeks before President-elect Donald Trump takes over the White House and possibly make good on his campaign promise to launch a major crackdown on illegal immigrants.

Citing figures from the Philadelphia-based New Sanctuary Movement, which counts Christian churches among its members, The Guardian reported that some 300 American churches have come forward in the past weeks offering to provide refuge to immigrants regardless of their status.

More than 1,000 people from Philadelphia alone have volunteered for the movement's "sanctuary in the streets" programme, from an initial number of just 65 volunteers.

Peter Pedemonti of the New Sanctuary Movement described the rise in the number of congregations offering refuge and asking how they can help immigrants as "pretty dramatic."

"The faith community has a specific role to stand up and speak out, and offering sanctuary is a bold way of doing that," Pedemonti told The Guardian.

He also noted how people have become "very scared" after Trump won the elections.

"There are waves of despair, anger and disbelief at Trump's election and the rise of white supremacism. This is a very shocking part of U.S. society that was in the shadows before, and with Trump it has come into the mainstream. It's very disturbing," he said.

Reverend Robin Hynicka of the United Methodist Church in Arch Street, Philadelphia also has the same observations, describing a state of anxiety that gripped immigrants just days after Trump emerged as the winner of the presidential polls.

He pledged that his church will provide space and support for immigrants who will seek refuge there.

"People are feeling more vulnerable than before. [But] people of faith and conscience are walking alongside the immigrant community. Sanctuary provides a moral alternative to what we think is an immoral policy," Hynicka told The Guardian.