Thousands of people gathered in Dallas to mark the 50th anniversary of the assassination of President John F Kennedy.

About 5,000 people arrived in Dealey Plaza to attend the first official memorial of the assassination to be held in the city, which has long struggled to cope with the legacy of JFK's death.

The crowd stood silent as singer Monica Saldivar walked on a stage flanked by the Dallas Police department honour guard and sang the American national anthem.

The stage was erected just metres from the Texas School Book Depository building where sniper Lee Harvey Oswald perched on a 6th floor windowsill on 22 November, 1963 and shot the president dead.

"A new era dawned and another was weaned half a century ago when hope and hatred collided here in Dallas," mayor Mike Rawlings told the crowd.

"President Kennedy has always been revered in our family," said Colleen Bonner, 41, one of the few thousand people who won the ballot that allocated tickets to attend the ceremony.

"I just wanted to honour his memory and I wanted to be a part of history."

Flags flew at half-staff and a minute's silence was observed across the country.

Earlier, attorney general Eric Holder paid his respects at Kennedy's grave at Arlington National Cemetery outside Washington.

Holder was followed by Jean Kennedy Smith, 85, the last surviving Kennedy sibling, who was accompanied by other family members to lay a wreath at her brother's grave.

"Today and in the decades to come, let us carry his [Kennedy's] legacy forward. Let us face today's tests by beckoning the spirit he embodied - that fearless, resilient, uniquely American character that has always driven our nation to defy the odds, write our own destiny, and make the world anew," said President Barack Obama.

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JFK Assassination 50th Anniversary
US President John F Kennedy was shot on 22 November, 1963 Reuters
JFK Memorial Plaza
A silhouette of John F Kennedy Jr saluting his father's casket at the JFK Memorial Plaza Reuters
Dealey Plaza JFK
Dealey Plaza remembers Reuters
Texas JFK
Crowds gather in Dealey Plaza for commemorative ceremonies marking the 50th anniversary of JFK's assassination Reuters
JFK Dallas
A video camera atop Dealey Plaza's "grassy knoll," records the crowds Reuters
Lee Harvey Oswald JFK
The sixth floor window of the Texas Book Depository, where Lee Harvey Oswald was positioned when he shot President John F Kennedy, Reuters
Barack Obama