Arizona shootings: US mourns dead after Giffords attack

Earlier, Mr Obama led the nation in a silent tribute from the South Lawn of the White House.

About 300 White House staff members joined the brief outdoor ceremony, bowing their heads as a marine honour guardsman rang a bell three times.

On the east steps of the Capitol building, hundreds of congressional staffers also paid tribute to Ms Giffords and the other victims of Saturday’s shooting.

The BBC’s Jonny Dymond, in Tucson, says small groups gathered in public spaces, in offices and in shops and stopped in silence for a minute.

This city did not come to a halt, our correspondent says, as many had done their mourning over the weekend in public vigils and private houses.

The crew on board the International Space Station (ISS) also paused for a brief silence. The commander on the ISS is Ms Giffords’ brother-in-law, Cmdr Scott Kelly. Her husband, Mark Kelly, is also an astronaut.

“”As I look out the window, I see a very beautiful planet that seems very inviting and peaceful,” said Cmdr Kelly. “Unfortunately, it is not.

“These days, we are constantly reminded of the unspeakable acts of violence and damage we can inflict upon one another, not just with our actions but also with our irresponsible words.

“We are better than this. We must do better.”

The Speaker of the House of Representatives, Republican John Boehner, called on fellow legislators to “stand together” and “rally round our wounded colleague”.