Federal agents spied on the widow of Martin Luther King Jr. for several years after his assassination in 1968, according to newly released documents that reveal the FBI worried about her following in the footsteps of the slain civil rights icon.

Coretta Scott King might try to tie "the anti-Vietnam movement to the civil rights movement" according to some of the nearly 500 pages of intelligence files, which go on to show how the FBI trailed King at public appearances and kept close tabs on her travel.

The documents were obtained by Houston television station KHOU in a story published Thursday. Coretta Scott King died in January 2006. She was 78.