Racial tension across America reached breaking point on this day in 1968 when Dr Martin Luther King Jr, the clergyman and campaigner who advocated non-violent civil rights activism by black Americans, was assassinated in the southern US city of Memphis, Tennessee.

Dr King, 39, was in the southern US city to support striking sanitation workers. He was shot through the neck by a rifle bullet at 6.01pm as he stood on the balcony of his hotel; though he was rushed to a nearby hospital, he did not regain consciousness and was pronounced dead at 7.05pm.

As news of his murder spread, rioting broke out in more than 100 cities across the country. 4,000 members of the National Guard were drafted into Memphis to keep the peace and a dusk-to-dawn curfew was imposed.

King (third from left) with (left to right) Hosea Williams, Jesse Jackson and Ralph Abernathy pictured on the balcony of the Lorraine Motel in Memphis, 24 hours before he was shot on the same spot.

Soon after the shooting, police found a bundle of belongings including a rifle and binoculars wrapped in a green blanket close to the hotel. Fingerprints on these were identified as those of an escaped convict, James Earl Ray, who had purchased the rifle under an alias six days earlier.

A worldwide manhunt for Ray followed. On June 8, 1968, he was arrested at London's Heathrow Airport while trying to leave the UK on a fake Canadian passport. Extradited to Tennessee for trial, he pleaded guilty to the assassination and was sentenced to 99 years in prison.

Dr King, a Baptist minister, had risen to prominence in the civil rights movement in the mid-1950s. He had survived previous attempts on his life, including the bombing of his house in the wake of his involvement in the Alabama bus boycott in 1955.

[Read more: August 28, 1963 - Martin Luther King delivers 'I Have a Dream' speech]

In August 1963, he led the March on Washington for Jobs and Freedom, which culminated with more than 250,000 demonstrators listening to his famous ‘I Have a Dream’ speech in front of the Lincoln Memorial. The following year, Dr King was awarded the Nobel Peace Prize.

Four days after his death, his widow Coretta led the couple's four children and a crowd estimated at 40,000 in a silent march through the streets of Memphis, in memory of her murdered husband. The next day, his funeral in his hometown of Atlanta, Georgia (pictured below) was broadcast on national television.

A brace of plow mules drawing the farm wagon bearing King's mahogany casket along the funeral procession route in Atlanta on April 9.

A procession of more than 100,000 mourners followed the clergyman's body as it was transported for three and a half miles through the streets of the city, from his church to his alma mater of Morehouse College.

Ray recanted his confession in prison and later claimed he had only been a minor part of a conspiracy to kill Dr King. He remained incarcerated until his death in 1998.

Also on this day: April 4, 1988 - Crossroads Motel checks out as much-maligned soap is axed by ITV