Former US congresswoman Gabby Giffords has made an emotional plea for Congress to take action to curb gun violence in the aftermath of last month's Connecticut school massacre.

Ms Giffords, who was seriously wounded in a shooting in Arizona in 2011, called on politicians to "be bold, be courageous".

Speaking haltingly, Ms Giffords was the first person to testify before the first congressional hearing on gun violence since the 14 December incident in which a gunman shot dead 20 children and six adults at an elementary school in Newtown, Connecticut.

Responding to outrage across the country following the Connecticut massacre, US President Barack Obama and other Democrats are seeking the largest gun-control package in decades.

"This is an important conversation for our children, for our communities, for Democrats and Republicans," Ms Giffords told the Senate Judiciary Committee.

"Speaking is difficult. But I need to say something important," she told the senators.

"Violence is a big problem. Too many children are dying - too many children. We must do something. It will be hard. But the time is now."

Accompanied by her husband, former astronaut Mark Kelly, she concluded: "You must act. Be bold, be courageous. Americans are counting on you. Thank you."

She did not take questions from the committee.

Mr Kelly also testified. The couple recently founded Americans for Responsible Solutions, a group intended to combat gun violence.

"Gabby and I are pro-gun ownership. We are also anti-gun violence. And we believe that in this debate, Congress should look not towards special interests and ideology, which push us apart, but towards compromise, which brings us together," Mr Kelly told the senators.

Others set to testify include National Rifle Association Executive Vice President and CEO Wayne LaPierre, whose group is an influential opponent of gun restrictions.

Mr Obama's proposals to curb gun violence include reinstating the US ban on military-style "assault" weapons, limiting the capacity of ammunition magazines, and more extensive background checks of prospective gun buyers, largely to verify whether they have a history of crime or mental illness.

Republicans and some pro-gun Democrats envision a more modest package.

It is unclear whether there is sufficient support in the Democratic-led Senate and the Republican-led House of Representatives to pass any gun restrictions beyond improved background checks.

Three shot at Arizona office complex

A gunman shot three people at an office complex in Phoenix, Arizona.

A police spokesman said the gunman remained at large. One of the victims was critically wounded.

The remaining two victims' injuries were less severe.

Authorities said police believe there was only one shooter.