The National Security Agency (NSA) spied on Martin Luther King Jr., Muhammad Ali, and other critics of the Vietnam War during the 1960s, according to classified documents revealed Wednesday. The spying program was discovered in the 1970s, when it was shut down, but its targets had never been known. The NSA also spied on journalists from The New York Times and The Washington Post, as well as two members of Congress.

Alarmed by the intensity of antiwar dissent, President Lyndon Johnson asked U.S. intelligence agencies if the protests had been masterminded by foreign powers, and to create “watch lists” of war critics.

The secret six-year spying program, dubbed "Minaret," later deemed "disreputable, if not outright illegal" had been exposed in the 1970s but the targets of the surveillance were kept secret until now.

The names of the NSA's targets are eye-popping: Civil rights leaders Dr. Martin Luther King and Whitney Young were on the watch list, as were heavy-weight boxing champion Muhammad Ali, New York Times journalist Tom Wicker, and veteran Washington Post humor columnist Art Buchwald. Also startling is that the NSA was tasked with monitoring the overseas telephone calls and cable traffic of two prominent members of Congress, Senators Frank Church (D-ID) and Howard Baker (R-TN).

The program continued after Richard Nixon entered the White House in 1969, and historians say it reflected a climate of paranoia pervading his presidency.

U.S. Attorney General Elliot Richardson shut down the NSA program in 1973, just as the Nixon administration was engulfed in scandal.

The documents were published on Wednesday after the government panel overseeing classification ruled in favor of researchers at George Washington University who had long sought the release of the secret papers.