Bloody Sunday: Thousands jam Selma bridge on 50th anniversary of civil rights clash

President Barack Obama, center, walks as he holds hands with Amelia Boynton Robinson, who was beaten during "Bloody Sunday," as they and the first family and others including Rep. John Lewis, D-Ga,, left of Obama, walk across the Edmund Pettus Bridge in Selma, Ala. for the 50th anniversary of “Bloody Sunday," a landmark event of the civil rights movement, Saturday, March 7, 2015. From front left are Marian Robinson, Sasha Obama. first lady Michelle Obama. Obama, Boynton and Adelaide Sanford, also in wheelchair. (AP Photo/Jacquelyn Martin) (The Associated Press)

President Barack Obama hugs Rev. Leodis Strong, Minister of Brown Chapel AME, after he said a closing prayer, while former President George W. Bush talks with Rep. John Lewis, D-Ga., by the Edmund Pettus Bridge in Selma, Ala., on the 50th anniversary of “Bloody Sunday," a landmark event of the civil rights movement, Saturday, March 7, 2015. (AP Photo/Jacquelyn Martin) (The Associated Press)

Lamar Dudley, of Selma, stands on the Edmund Pettus Bridge after a speech by President Barack Obama, Saturday, March 7, 2015, in Selma, Ala. This weekend marks the 50th anniversary of "Bloody Sunday," a civil rights march in which protesters were beaten, trampled and tear-gassed by police at the Edmund Pettus Bridge in Selma, Ala. (AP Photo/Bill Frakes) (The Associated Press)

Thousands of people have crowded on and around an Alabama bridge, commemorating bloody clashes 50 years ago between police and demonstrators during the civil rights struggle.

Associated Press reporters at the scene in Selma said thousands jammed shoulder to shoulder, many not moving as they held up signs and some chanted or sang hymns. They said some groups managed to cross earlier.

"Black lives matter, all lives matter," read one sign raised in the crowd, which was commemorating the anniversary.

Police estimated at least 15,000 to 20,000 people were present.

On March 7, 1965, police beat and tear-gassed marchers at the foot of the bridge in Selma in a spasm of violence that shocked the nation. The attack help build momentum for passage of the Voting Rights Act later that year.