New US gun laws to make background checks mandatory

US President Barack Obama is to widen background checks on buyers of firearms, in a series of measures to address gun violence.

The plans will be announced on Tuesday by the president, despite opposition from Congress to new gun laws.

All sellers who operate online or at gun shows will be forced to conduct background checks on potential buyers.

Republican presidential candidate Rand Paul said he would fight the executive actions "tooth and nail". Several of his Republican rivals said they would erase the measures "on day one" if they win the White House.

But Obama says his new measures will be within his legal authority and consistent with the Second Amendment, which grants Americans the right to bear arms.

And while they will not solve every violent crime in the US, he said, they will potentially "save lives and spare families the pain" of loss.

Under the plan announced on Monday evening by the White House, all sellers must be licensed and conduct background checks, overturning current exemptions to some online and gun show sellers.

States must provide information on people disqualified due to mental illness or domestic violence and the FBI will increase the workforce processing background checks by 50%, hiring more than 230 new examiners.

Congress will be asked to invest $500 million to improve access to mental healthcare, and the departments of defence, justice and homeland security will explore "smart gun technology" to improve gun safety.