It is reported that the 28, including women and children, have not been seen or heard from since they were detained on Friday 12th September.
Bibles were destroyed by the authorities from the Commission for the Promotion of Virtue and the Prevention of Vice as officials disrupted the meeting.
It is thought that believers had gathered at a house in the eastern city of Khafji.
Speaking to America's Fox News, director of the Hudson Institute's Center for Religious Freedom, Nina Shea, said: "Saudi Arabia is continuing the religious cleansing that has always been its official policy.
"It is the only nation state in the world with the official policy of banning all churches.
"This is enforced, even though there are over two million Christian foreign workers in that country. Those victimised are typically poor, from Asian and African countries with weak governments."
Fox News says a spokesperson for the Saudi government claimed to have no knowledge of the arrests, but several newspapers in the country have reported the story.